________ a foreign language is great fun for me.
A:Learn
B:Learning
C:learned
D:learns
- Could you tell me ________ he comes here?
- He drives here himself(他自己).
图示为中枢神经系统和膝跳反射模式图,请据图回答:
现有一种无色的营养液,可能由硝酸钙、碳酸钾、硝酸钾、氯化钾中的一种或几种物质组成,为探究其成分,某同学设计并完成了如图所示的实验.
根据以上实验,请你进行有关推断.