句型What are you doing? I'm... — 英语词汇题
题目
用所给动词的 -ing 形式补全句子（每空一词）。1. —What are you doing? —I'm r______（read 的 -ing 形式）a book. 2. —What are you doing? —I'm w______（write 的 -ing 形式）a letter. 3. —What are you doing? —I'm s______（sing 的 -ing 形式）an English song.