Question:
Which position did Sir John Arbuthnot, 1st Baronet hold in May, 1950?

Context:
 Sir John Arbuthnot, 1st Baronet holds the position of Member of the 41st Parliament of the United Kingdom from May, 1955 to Sep, 1959. 
 Sir John Arbuthnot, 1st Baronet holds the position of Member of the 40th Parliament of the United Kingdom from Oct, 1951 to May, 1955. 
 Sir John Arbuthnot, 1st Baronet holds the position of Member of the 39th Parliament of the United Kingdom from Feb, 1950 to Oct, 1951. 
 Sir John Arbuthnot, 1st Baronet holds the position of Member of the 42nd Parliament of the United Kingdom from Oct, 1959 to Sep, 1964.

Answer:
Member of the 39th Parliament of the United Kingdom