常温下单质硫主要以S8形式存在。加热时,S8会转化为S6、S4、S2等。当温度达到750 ℃时,硫蒸气主要以S2形式存在(占92%)。下列说法正确的是( ) A.S8转化为S6、S4、S2属于物理变化 B.不论哪种硫分子,完全燃烧时都生成SO2C.常温条件下单质硫为原子晶体 D.把硫单质在空气中加热到750 ℃即得S2The last time I
________ Jane she ________ cotton in the fields.
A. had seen; was
picking
B. saw; picked
C. had seen; picked
D. saw; was picking