Unit 12 Section B (3a—self-check)一、选择填空题 ( )1. It __________ sunny today, but it __________ cloudy yesterday. A. is, is B. was, was C. is, was D. was, is( )2. I ___________ at school now, but I _________ at home an hour ago. A. am, am B. was, was C. am, were D. am, was( )3...