This river is so big that it is impossible to build a _______ under it without modern technology.

This river is so big that it is impossible to build a _______ under it without modern technology.
a、canal
b、 tunnel
c、 channel
d、 cable
这题选什么？为什么？请翻译整句 谢谢

This river has changed 为什么This is不能简写This's 1.This is no fish in this river because it has been polluted(保持原句） What`s this?回答是This is a chair.还是It`s a pencil. this is the bus _______the people's park. 单选--Is this Mr.White`s office,Mary? ( )3.-What’s this in English?A. This is a bag B. It is bag. C. It’s a bag. 1.This is the third time this week he's had to study late,_? who's this? This is my father\mother\sister\brother\friend This is Jack's bookcase .(保持原意）This ________ ___________ ________Jack.