He often chats on the phone with his friend.(用at the moment改

often是指通常的状态,所以chat用一般现在时表示
at the moment特指在某个时刻,所以chat用现在进行时表示
改写后的句子应为：
He is chatting on the phone with his friend at the moment
这题主要是用来考查对句子时态的转换