Question

As the immune system weakens, it loses the ability ________ illnesses.

A．fighting	B．fought
C．to fight	D．to be fought

Answer 1

C

C　考查非谓语动词。句意：由于免疫系统衰退，它失去了与疾病抗争的能力。表示“……的能力”，要用不定式作后置定语来修饰the ability。