下面是某初中课堂教学片段。

T: (referring to a picture) where is John, Li Lei?

Sl: He has gone to Shanghai.

T: How many times has he been to Shanghai?

Sl: He has been to Shanghai for only once.

T: (referring to another picture) where is Mary, Wang Wei?

S2: She has gone to the library.

T. How many times has she been to the library a week?

S2: She has been to the library twice a week. 

根据上面所提供的信息，从下面四个方面作答：