神经—肌接头处的化学递质是
A.肾上腺素B.去甲肾上腺素C.5-羟色胺D.乙酰胆碱E.二酰甘油
参考答案:D
The calculations, had they been done by hand, ______all practical value by the time they were finished.
A.had lost
B.would lose
C.should have lost
D.would have lost
哪些材料适用电解浸蚀?为什么?