Rose can't go with us.let's ask mary_____.正解是instead,但是instead前面要不要to呢,请解释要或不要的原因.

Rose can't go with us. let's ask mary instead.
为什么要加 "to" ? Instead 不是动词.
(1) Having planned to drive, we walked instead.
(2) Forget about dieting and eat normally instead.
(3) I don't like coffee. Could I please have tea instead?