—Could you come to my birthday party?—Sorry, I ________.
A:couldn't
B:can't
C:can
小量程的电流表G和用与此相同的小量程电流表改制成的电流表A,电压表V的内阻分别为RG、RA、RV,它们之间的大小关系是( )
The __________ of the sofa is high, we don’t have enough money to buy it.
如图,为估算某河的宽度,在河对岸选定一个目标点A,在近岸取点B,C,D,使得AB⊥BC,CD⊥BC,点E在BC上,并且点A,E,D在同一条直线上.若测得BE=20m,CE=10m,CD=20m,则河的宽度AB等于( )