题目

根据句意，用括号内所给单词的适当形式填空。 1. It’s _________(sun) today. 2. It’s _________(rain) in this city now. 3. Could I drink some _________(juice)?  4. The teacher asks _________(he) to get to school on time.  5. Look! My pet dog is _________(sit) on the chair.  答案：1. sunny  2. raining 3. juice  4. him 5. sitting下列关于育种的叙述中，正确的是                              （   ）A．用物理因素诱变处理可提高突变率B．诱变育种和杂交育种均可形成新的基因C．三倍体植物不能由受精卵发育而来D．诱变获得的突变体多数表现出优良性状