Don’t stand by when you come across have difficulty in supporting their family because of

问题补充：

Don’t stand by when you come across have difficulty in supporting their family because of serious illness.

A. Who

B. Whoever

C. Whichever

D. Whomever

答案：

A. Who

(答案→)B. Whoever

C. Whichever

D. Whomever

解析：句意：当你遇到因为重病难以养家糊口的人不要袖手旁观。这里come across后面是宾语从句，宾语从句中缺少主语用whoever引导宾语从句，相当于anyone who，whomever在从句中做宾语，whichever“无论哪个”，who引导宾语从句的意思是“谁”，所以选B。