1.b (let sb be followed by verb prototype)
2.a (wanting to do something means "wanting to do something")
3.c (receiving a letter from someone means "receiving a letter from someone")
4.d (fixed collocation, at+time point, at+week)
5.c (don't want to do something) means "don't want to do something"; "Want to do something" means "want to do something")
In Britain, children always buy birthday presents together. )
I often don't eat chocolate because it is unhealthy. )
Haven't you ever skated?
-Yes, I never skate. Analysis: This dialogue is an antonym question, which is interpreted according to the opposite meaning in translation, but the English form should still abide by the rules of "yes, I do" and "no, I don't want to". )
Third,
1. always (I often go to my grandparents' house for dinner on Saturday)
My father never smokes, because smoking is harmful to health.
3. Under normal circumstances; Sometimes (Spring Festival is usually in February, but sometimes in January)
4. Always (please raise your hand when you want to speak in class)