His parents were so poor that they couldn’t to buy a computer for their only son .A. payB

问题补充：

His parents were so poor that they couldn’t to buy a computer for their only son .

A. pay

B. cost

C. spend

D. afford

答案：

A. pay

B. cost

C. spend

(答案→)D. afford

解析：考查动词。afford付得起之意，句意：他父母如此的穷以至于他们付不起为他们唯一儿子买电脑的钱。