Pollution/ be/ most/ serious/ problem/, / not/ is?
 A.
 Pollution is most serious problem, isn’t it?
 B.
Pollution is the more serious problem, isn’t it?
 C.
Pollution is the most serious problem, isn’t it?
D.
 Pollution is most serious as problem, isn’t it?

Giải thích : Đây là câu so sánh nhất : S + is / are / am + the + adj est / most + adj

                  Và là câu hỏi đuôi: vế trước khẳng định `->` vế sau phủ định (is `->` isn't/ is not)

Pollution$/$be$/$most$/$serious$/$problem$/,/$not$/$is?

`=>`Pollution is the most serious problem, isn't it?

$-$Pollution`=>`be`->`is

$-$most serious`->`the most serious

$-$not is`->`isn't

Ta chọn đáp án $C.$

$\text{@ThanhTruc2008}$