In this institution, a medal, together with a prize of a certain sum of money, ________ does best in science and technology every two years.

A．is given to whoever

B．are given to anyone

C．are given to who

D．is given to whom

利用香豆素的挥发性，可采取的提取方法是（）

A．加热冷凝法 

B．石油醚或乙醚回流提取法 

C．碱水加热提取加酸沉淀法 

D．水蒸气蒸馏法 

E．硅胶层析法