---Let's go shopping this evening.
---________. I want to buy some fruit.
A:Good idea.
B:Thanks.
C:No, I can't.
使用高倍镜观察装片的步骤是( )①转动转换器把低倍物镜移走,换上高倍镜 ②在低倍镜下找到目标③将目标移到视野中央 ④调节细准焦螺旋和反光镜,直到视野适宜、物像清晰为止
已知向量a→=(2,1),b→=(3,λ),若a→⊥b→,则λ=____