The soft music sounds ____. We are all listening ____.
A:beautiful; carefully
B:noisy; carefully
C:happily; careful
冬天,电热水壶将水烧开时,冒出大量“白气”,这是由于水蒸气发生____ 形成的,阳光透过“白气”,出现彩虹,这是光的____现象.