下列物质性质与应用对应关系正确的是
| A．氨气具有还原性，可用作制冷剂 |
| B．Na2O2呈浅黄色，可用作潜水艇中的供氧剂 |
| C．明矾水解形成Al(OH)3胶体，可用作水处理中的净水剂 |
| D．碳酸钠溶液显碱性，可用作锅炉除垢时CaSO4沉淀的转化剂 |
Progress______ so far very good and we are sure that the work will be finished on time.
| A．was | B．had been | C．has been | D．will be |
Charles was alone at home, with_______ looking after him.
| A．someone | B．anyone | C．not one | D．no one |
It is often ______ that human beings are naturally equipped to speak.
| A．said | B．to say | C．saying | D．being said |
I can’t leave. She told me that I ______ stay here until she comes back.
| A．can | B．must | C．will | D．may |
—— Do you mind my opening the window? It’s a bit hot in here.
—— ______ , as a matter of fact
| A．Go ahead | B．Yes, my pleasure |
C．Yes, I do | D．Come on |