A.We are just looking.
B.Mind your own business.
C.We will order later.
D.Take care of yourself.

A.OK. No problem.
B.The same to you.
C.Yes, that's a good idea.
D.Thank you.

A.Yes, I'd like to.
B.OK. What's the matter?
C.That's great. Congratulations.
D.Well, you are right.

A.4HF + SiO2 ⟶ Si + 2H2O + 2F2.
B.3HF + Na2SiO3 ⟶ 2NaF + SiF + 3H2O.
C.4HF + SiO2 ⟶ SiF4 + 2H2O.
D.4HF + Na2SiO3 ⟶ 2NaOH + SiF4 + H2O.

A.4HF + SiO2 ⟶ Si + 2H2O + 2F2.
B.3HF + Na2SiO3 ⟶ 2NaF + SiF + 3H2O.
C.4HF + SiO2 ⟶ SiF4 + 2H2O.
D.4HF + Na2SiO3 ⟶ 2NaOH + SiF4 + H2O.

A.96%.
B.78%.
C.84%.
D.91%.

A.26,61.
B.25,96.
C.23,18.
D.29,57.

A.
B.
C.
D.

A.
B.
C.
D.

A.I feel very bored
B.You’re welcome
C.I don’t agree. I’m afraid
D.That would be great