【多选题】一节课或完成阶段性教学内容以后,说一段小结语,很有必要,其作用有( )。
【单选题】消极强化可以使相应的条件反应出现的概率( )。
【判断题】判断题:( )4、盘式制动器有自动刹紧作用。
【单选题】鱼类身体分为头、躯干、尾3部分,尾部为()
【单选题】Last week, I went to _____ and I took lots of photos. [ ]
【单选题】___ photos, and I often ___ photos of flowers in spring.
【单选题】I take photos of people and nature. I am a _____
【单选题】I______photos,and I often ______photos of flowers in sping.