He failed the exam ________he was too careless.

(2013·安徽安庆二模)—She looks very happy. She ________ have passed the exam.—I guess so. It’s not difficult after all.

I can’t find my dictionary.—Don’t worry about your lost book. You can use _______.

对下列句子中加点词语或文言句式的解释，有误的一项是

How_________I help them to underst