以硼氢化合物NaBH4（B元素的化合价为+3价）和H2O2作原料的燃料电池，负极材料采用Pt/C，正极材料采用MnO2，其工作原理如图所示。下列说法正确的是 
| A．电池放电时Na+从b极区移向a极区 |
| B．每消耗3 mol H2O2，转移的电子为3 mol |
| C．电极a采用MnO2，MnO2既作电极材料又有催化作用 |
| D．该电池的负极反应为：BH4－＋8OH－－8e－=BO2－＋6H2O |
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 |