Please answer the following question: Information:  - The Royal Navy (RN) is the United Kingdom's naval warfare force. Although warships were used by the English kings from the early medieval period, the first major maritime engagements were fought in the Hundred Years War against the kingdom of France. The modern Royal Navy traces its origins to the early 16th century; the oldest of the UK's armed services, it is known as the Senior Service.  - John St Aubyn , 1st Baron St Levan ( 23 October 1829 -- 14 May 1908 ) , known as Sir John St Aubyn , 2nd Baronet , from 1872 to 1887 , was a British Liberal , and later Liberal Unionist , politician who sat in the House of Commons from 1858 until 1887 when he was raised to the peerage .  - The Grenadier Guards (GREN GDS) is an infantry regiment of the British Army. It is the most senior regiment of the Guards Division and, as such, is the most senior regiment of infantry. It is not, however, the most senior regiment of the Army, this position being attributed to The Life Guards. Although The Coldstream Guards were formed before The Grenadier Guards, the regiment is ranked "after" the Grenadiers in seniority as, having been a regiment of the New Model Army, the Coldstream served the Crown for four fewer years than the Grenadiers (the Grenadiers having formed as a Royalist regiment in exile in 1656 and the Coldstream having sworn allegiance to the Crown upon the Restoration in 1660).  - Baron St Levan, of St Michael's Mount in the County of Cornwall, is a title in the Peerage of the United Kingdom. It was created on 4 July 1887 for the former Member of Parliament Sir John St Aubyn, 2nd Baronet. He had previously represented Cornwall West in House of Commons as a Liberal and St Ives as a Liberal Unionist. He was succeeded by his eldest son, the second Baron. He was a Colonel and Honorary Brigadier-General in the Grenadier Guards. On his death the titles passed to his nephew, the third Baron. He was the son of the Hon. Sir Arthur James Dudley Stuart St Aubyn (18671897), second son of the first Baron. The third baron was succeeded in 1978 by his eldest son, the fourth baron. Before inheriting the peerage the fourth baron served with the Royal Navy at Dunkirk and in a minesweeper in Arctic Convoys during World War II and was awarded the Distinguished Service Cross (DSC). As of 2014, the titles are held by the latter's son, the fifth Baron, who succeeded in 2013.    After reading the paragraphs above, we are interested in knowing the entity with which 'john st aubyn' exhibits the relationship of 'military branch'. Find the answer from the choices below.  Choices: - british army  - coldstream guards  - infantry  - navy  - royal navy
A:
british army