1. The aim of the conference is to promote international (friends)friendship.

2. Donald is so ( create)creative in the kitchen. I think he should be a professional chef.

3. The keys were locked inside the car. (Luck)Luckily, a side window was open.

4. They have agreed to ( wide)widen the road because of the amount of heavy traffic now using it.

5. Hasn't anyone ever told you that it's very (polite)impolite to interrupt when other people are talking?

6. I told the manager that it was the (bad)worst hotel I had ever stayed in.

7. The headmaster is going to make a ( speak )speech in front of the teaching staff.

8. Experienced (travel) travelers will enjoy our hotel's comfortable double rooms.

9. That big dog is perfectly ( harm)harmless. It has never been known to attack anyone.

10. " Well, Mrs. Tuner, you'll be pleased to hear that Georgia has made a big (improve)improvement in physics".

1. It is difficult to learn English.

2. It was wonderful to see our friends again.

\(n_{CaCO_3}=\dfrac{200}{100}=2\left(mol\right)\)  

\(CaCO_3+2HCl\xrightarrow[]{}CaCl_2+H_2O+CO_2\)

    \(2\)                                                      \(2\)    (mol)

\(V_{CO_2}=2.22,4=44,8\left(l\right)\)

had started

D. take

to take a look at:ngắm/nhìn/xem

became/being sent

invented