一静止的 ${}_{92}^{238}$ U核经α衰变成为 ${}_{90}^{234}$ Th，释放出的总动能为4.27MeV．问此衰变后 ${}_{90}^{234}$ Th核的动能为多少MeV（保留1位有效数字）？

选用方框中的句子完成对话，其中有两项是多余的。
Li Lei: Excuse me. ____
Mr. Smith: Yes. And you are.. . ?
Li Lei: I’m Li Lei. Your friend Miss Wu is busy at the moment. She asks me to meet you. Welcome to Hangzhou, Mr. Smith.
Mr. Smith: Thank you.
Li Lei: By the way____ 
Mr. Smith: No. This is my second time. I came here in 1998 for the first time.
Li Lei:____
Mr. Smith: I like it very much. It’s very beautiful and famous in the world. And the people here are quite friendly.____
Li Lei: I’m glad you like the city. And now Hangzhou is becoming more and more beautiful.____
Mr. Smith: I think so. Thank you very much for meeting me.
Li Lei: It’s a pleasure.