下列哪项是生物多样性中最直观的体现( )
A:物种多样性
B:遗传多样性
C:生态系统多样性
D:环境多样性
Everyone in the tourist industry has made the point that __________ Government assistance is helpful, what they actually need most is for the visitors themselves to return.
太阳能是一种清洁的新能源,目前人们对其利用越来越广泛。下列属于人类对太阳能间接利用的是( )
填一填