China is a mountainous country.Hills,mountains,and plateaus cover _______ of the total area.
A. 1/3
B. 3/4
C. 2/3
D. 1/2
进行TC4重要用途铸锭一次Φ622mm熔化,工艺规程规定漏气率为()
A. ≤1.07Pa/min
B. ≤0.93Pa/min
C. ≤0.8Pa/min
D. ≤0.67Pa/min
It’s high time we _____ cutting down the rainforests.
A. stopped
B. had to stop
C. shall stop
D. stop
理论构思实质是一种有待检验证明的()
A. 科学论点
B. .研究课题
C. 研究问题
D. 理论假设