属于第二类精神药品的是()
A.曲马多
B.美沙酮
C.司可巴比妥
D.麦角新碱
参考答案:A
解析:美沙酮是麻醉药品;司可巴比妥是第一类精神药品;曲马多是第二类精神药品。
22.After playing in the park for a few hours, the pupils gathered under trees _______shade and
________ down to eat their picnic lunch.
A.provided; sit
B.provided; sat
C.providing; sitting
D.providing; sat
何谓热电偶?