钢筋混凝土预制桩应在混凝土达到设计强度的（）方可起吊 A.50% B.70％ C.8

A: When did you first go swimming?
B: When I was 5 years old.
A: 1
B: I felt very nervous and frightened.
A: Me, too. I went swimming with my elder brother for the first time. 2 So I cried to go home as soon
as we arrived at the swimming pool. What happened to you next?
B: 3 Then he began teaching me how to swim in the water near the beach.
A: 4
B: No. It was rather hard. 5
A: And now you are the best swimmer in our class.
B: Yeah. I'll practice harder in the future.