The mother was anxious . . . . . . . . the safety of her son.

A. upon

B. about

C. at

D. for

Answer: Option B

Solution(By Examveda Team)

Normally, 'anxious about' and 'anxious at' are used to express concern. 'Anxious about' refers to the subject of worry, and 'anxious at' refers to the cause of worry.