不属于马铃薯中所含的有毒物质是（）。A、龙葵素 B、香豆素 C、植酸酶 D、单宁

Are those         ?           [ ]

A. potato  

B. potatoes             

C. potatos

Kate is not able ________the party because she is ill.

A．comes

B．come

C．to come to

D．coming

— If he _____, he _____ that poisonous food.

— Luckily he came back to life immediately. [ ]

A. was warned; would not take

B. had been warned; would not have taken

C. would be warned; had not taken

D. would have been warned; had not taken

建筑钢材的伸长率与（）标准拉伸试件标距间长度的伸长值有关。

A.到达屈服应力时

B.到达极限应力时

C.试件塑性变形后

D.试件断裂后

牙嵌式离合器只能在（）接合。

A.单向转动时

B.高速转动时

C.正反转工作时

D.两轴转速差很小或停车时