Đáp án cần chọn là: B
M = 1 2 1.2 . 2 2 2.3 . 3 2 3.4 ..... 99 2 99.100 . 100 2 101 = 1 2 .2 2 .3 2 ....99 2 .100 2 ( 1.2 ) . ( 2.3 ) . ( 3.4 ) .... ( 99.100 ) . ( 100.101 ) = ( 1.2.3.....99.100 ) . ( 1.2.3....99.100 ) ( 1.2.3.....99.100 ) . ( 2.3....99.100 ) .101 = 1 101