It’s true that （) you have a bad habit, you will find it difficult to giveit up.

According to the passage,which of the following is true？ ()

A． Tell the truth,even when you are wrong．

B． Keep some animals to kill them．

C．Look down on new ideas．

D． Everything on the Internet is good for children．

A.as

B.if

C.while

D.that

A.It's very nice of you

B.You're welcome

C.Thank you

D.The same to you

A.take

B.have

C.buy

D.has

– It’s our great pleasure to have you visit our company. --_________________

A、Thank you.

B、Nice to meet you.

C、It’s our pleasure, too.

D、Wonderful.

– How much is the air ticket？ -- ________________

A、It’s 150 dollars.

B、Which flight do you like？

C、Nice talking with you.

D、See you.

--- Is dinner ready, Carol？

--- ______.

A. It’s nearly ready

B. I’m hungry

C. Fine, thank you.

().Please call me Mary. That's my first name.

A. How are you

B. How shall I address you

C. Are you Mary

已知平面流动的速度为直线分布，若y_o=4m，好u_o=80m/s，试求：(1)函数ψ;(2)流动是否为有势流动。