在臭氧发生装置中装入氧气100mL，经反应：3O2 ＝2O3，最后气体体积变为95mL（体积均在标准状况下测定），则混合气体的密度是 （ ）
| A．1.3g/L | B．1.5g/L | C．1.7g/L | D．2.0g/L |
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 |