()与长期使用含有光敏物质的化妆品有关。
A、雀斑
B、色素痣
C、老年斑
D、瑞尔黑变病
参考答案:D
The old man sat in front of the television every evening, happy______ anything that happened to be on.
A.to watch
B.watching
C.watched
D.to have watched
某导体的电阻是2Ω,当通过1A电流时,导体的功率是__________W。通电1min时,导体上产生的热量是__________ J。