【单选题】(paragraph 5) Solar energy is unlimited but
A.
is very expensive to use.
B.
is air-polluting and costly.
C.
is unreliable& expensive to produce.
D.
is environmentally unfriendly
【判断题】Solar energy is believed to the ultimate energy source from the external sphere.
【单选题】每搏输出量和外周阻力不变而心率加快时,动脉血压的变化主要是
【单选题】Solar energy is ________
C.
in high energy density
【单选题】每搏输出量和外周阻力不变而心率加快时,动脉血压的主要变化是
【单选题】Only a small portion of solar energy is now being used by us.
【简答题】在每搏输出量和外周阻力不变而心率加快时,动脉血压的变化主要是 ( )
【单选题】Only a small portion of solar energy is now being used by us.
【单选题】刮水器某个档位不工作 , 以下可能的原因是 ( )