B.
–xiaqu
下去
, indicating continuation of an action in the future.
Ràng tā
shuō
xiàqu
.
让他说下去。
Let him go on (talking).
Yàoshì zhèyàng
liàn
xiàqu
, nǐ huì xué de hěn hǎo.
要是这样练下去,你会学得很好。
If you keep practicing like this, you will study well.