一人以每分钟60米的速度沿铁路步行,一列长144米的客车对面开来,从他身边通过用了8秒钟,列车的速度是____ 米/秒.
牛的体细胞中含有30对染色体,那么牛的卵细胞中和受精卵中分别含有的染色体数是 ( )
I hate to _____ some chores, but I like to______ my bed.
57=5×27×2=1014
B: During the first days of the Spring Festival holiday, pollution levels aren't ____ ____ ____ they were last year.