It's a day __mothers \ A.thank B.thanks C.thanking D.to thank 要原因的

It's a day __mothers \ A.thank B.thanks C.thanking D.to thank 要原因的
It's a day __mothers \ A.thank B.thanks C.thanking D.to thank 要原因的

It's a day __mothers \ A.thank B.thanks C.thanking D.to thank 要原因的
选D
是固定句式,it is + to do sth