what great fun it is+动词不定式
What great fun it is to swim in the river!
到河里游泳是多么有趣!Swimming in the sea is great fun.
在海里游泳很好玩。what great fun it is to greet those bears by shaking hands.
greet 后的 to 应该去掉 因为动词 greet 不需要介词 to
He sent his greetings to you in the letter.
他在这封信里向你致以问候。Give my greetings to her and hers.
请向她和她的家人问好。