下列元素在自然界只能以化合态形式存在的是
A.氧
B.硫
C.钠
D.氮
答案:C
性质活泼的钠在自然界中没有游离态,只能以化合态形式存在。氧、硫、氮有游离态,C正确。
The Golden Gate Bridge is a famous landmark in San Francisco. The USA. Which of the following words
is created in the same way as the word landmark?[ ]
A. unpleasant
B. useless
C. summertime
D. surprising
肝移植术后急性排斥反应最早在术后()。