In the mass extinction 65 million years ago, ______ of all species on earth vanished.

A．Because he was a Briton who adored American politics.
B．Because he liked to read American newspapers.
C．Because he lectured on the importance of friendship between U.S. and Britain.
D．Because he chose to live close to Americ

A．a historian
B．a reporter
C．Leacock's colleague
D．a Navy officer