Definition: 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.
Input: Passage: Dr. Jan Żabiński is director of the Warsaw Zoo, one of the largest in 1930s Europe, assisted by his wife, Antonina. 
On September 1, 1939, the aerial bombardment of Warsaw and Invasion of Poland commences. Antonina and her son Ryszard (Timothy Radford and later, Val Maloku) barely survive. As Polish resistance collapses, Dr. Lutz Heck, head of the Berlin Zoo and Adolf Hitler's chief zoologist and Jan's professional rival, visits the zoo while Jan is away. He offers to house the prized animals until after the war, later returning with Nazi soldiers to shoot the rest. He develops a romantic interest in Antonina.
The Jews of Warsaw are forced into the Ghetto. The Żabińskis' Jewish friends, Maurycy Fraenkel and his partner Magda Gross, seek a safe place for a friend's insect collection. Antonina offers to shelter Magda. Knowing they can be executed for helping Jews, Jan and Antonina decide to use the zoo to save more lives.
They seek out Heck to propose turning the abandoned zoo into a pig farm to feed the German occupying forces, secretly hoping to bring food to the Ghetto. Heck, in need of a new site for his experiments in recreating Aurochs as a symbol of the Reich, agrees.
Jan collects garbage from the Ghetto for the pigs and sees Jews starving. He begins working with the Underground Army to transport Jews to safehouses throughout the country. Jews are hidden in the zoo's cages, tunnels, and inside the Żabińskis' house. After some trepidation, Antonina agrees to help.
The Żabińskis continue smuggling Jews out of the Ghetto. In 1942, the Germans begin deporting Jews to death camps. Jan has no choice but to help load them into cattle cars under the Germans' watch.
Output:
Who is Ryszard's father?