核心问题
——I'll be away on a business trip. Would you mind looking after my cat? ——Not at all.
A. I've no time B. I'd rather not C. I'd like it D. I'd be happy to(全国高考,95-30)
答案为 D。但是，I'd be happy to. 似乎并不是完整的句子。
词典解答
上面的句子省略了 look after your cat。省略在各类英语试题中多次出现，这说明它是英语里很重要的语法现象。