Question

【题目】Write a letter to a friend, has some difficulties with his studies.

Answer 1

【答案】who
【解析】句意：给一位朋友写封信，他在学习上有些困难。这里构造非限制性定语从句，用who指代上文的a friend，并在非限制性定语从句中作主语。所以答案是who。