A:两灯实际功率之比为4:1
B:当电压U为18V时,灯L1、L2均正常发光
C:灯L2两端电压与电压U之比为1:5
D:电压U的最大值为15V
Jane has ______ from school for 2 years. When she ______ the happy time, she always misses her teachers and classmates.
如图所示曲线分别表示人体血液中CO2和O2相对含量的变化,则B段血管是____ 。
某海峡位于两大洲之间,又位于两大洋之间,则该海峡是( )