In this task, you're given passages that contain mentions of names of people, places, or things. Some of these mentions refer to the same person, place, or thing. Your job is to write questions that evaluate one's understanding of such references. Good questions are expected to link pronouns (she, her, him, his, their, etc.) or other mentions to people, places, or things to which they may refer. Do not ask questions that can be answered correctly without understanding the paragraph or having multiple answers. Avoid questions that do not link phrases referring to the same entity. For each of your questions, the answer should be one or more phrases in the paragraph, and it should be unambiguous.

Example input: Passage: Nearing London, Oliver encounters Jack Dawkins, a pickpocket more commonly known by the nickname the "Artful Dodger", and his sidekick, a boy of a humorous nature named Charley Bates, but Oliver's innocent and trusting nature fails to see any dishonesty in their actions. The Dodger provides Oliver with a free meal and tells him of a gentleman in London who will "give him lodgings for nothing, and never ask for change". Grateful for the unexpected assistance, Oliver follows the Dodger to the "old gentleman's" residence. In this way Oliver unwittingly falls in with an infamous Jewish criminal known as Fagin, the gentleman of whom the Artful Dodger spoke. Ensnared, Oliver lives with Fagin and his gang of juvenile pickpockets in their lair at Saffron Hill for some time, unaware of their criminal occupations. He believes they make wallets and handkerchiefs.
Example output: Who believes Fagin's gang make wallets and handkerchiefs?.
Example explanation: This question is based on the following sentence in the passage "He believes they make wallets and handkerchiefs". It evaluates the understanding that the pronoun "he" refers to name "Oliver". You can ask questions like this one about most pronouns in a paragraph.
Q: Passage: During the early part of the Second World War, Britain had a nuclear weapons project codenamed Tube Alloys. At the Quebec Conference in August 1943, the Prime Minister of the United Kingdom, Winston Churchill, and the President of the United States, Franklin Roosevelt, signed the Quebec Agreement, which merged Tube Alloys with the American Manhattan Project to create a combined British, American and Canadian project. The September 1944 Hyde Park Aide-Mémoire extended commercial and military cooperation into the post-war period. Many of Britain's top scientists participated in the Manhattan Project. The Quebec Agreement specified that nuclear weapons would not be used against another country without mutual consent. On 4 July 1945, Field Marshal Sir Henry Maitland Wilson agreed on Britain's behalf to the use of nuclear weapons against Japan.The British government considered nuclear technology to be a joint discovery, and trusted that America would continue to share it. On 16 November 1945, President Harry S. Truman and Prime Minister Clement Attlee signed a new agreement that replaced the Quebec Agreement's requirement for "mutual consent" before using nuclear weapons with one for "prior consultation", and there was to be "full and effective cooperation in the field of atomic energy", but this was only "in the field of basic scientific research". The United States Atomic Energy Act of 1946 (McMahon Act) ended technical cooperation. Its control of "restricted data" prevented US allies from receiving any information. Fearing a resurgence of American isolationism, and Britain losing its great power status, the UK government restarted its own development effort, now codenamed High Explosive Research.In 1949, the Americans offered to make atomic bombs in the US available for Britain to use if the British agreed to curtail their atomic bomb programme. This would have given Britain nuclear weapons much sooner than its own target date of late 1952. Only those bomb components required by war plans would be stored in the UK; the rest would be kept in the US and Canada. The offer was rejected by the British Chiefs of Staff on the grounds that it was not "compatible with our status as a first class power to depend on others for weapons of this supreme importance". As a counter-offer, they proposed limiting the British nuclear weapons programme in return for American bombs. The opposition of key American officials, including the United States Atomic Energy Commission's Lewis Strauss, and Senators Bourke B. Hickenlooper and Arthur Vandenberg, coupled with security concerns aroused by the 2 February 1950 arrest of the British physicist Klaus Fuchs as an atomic spy, resulted in the proposal being dropped.
A:
What are the last names of the American senators that opposed the counter-offer to the offer rejected by British Chiefs of Staff?