某主族元素R的最高价氧化物对应的水化物的分子式是H2RO4,该元素在周期表中位于( )
Progress______ so far very good and we are sure that the work will be finished on time.
Charles was alone at home, with_______ looking after him.
It is often ______ that human beings are naturally equipped to speak.
I can’t leave. She told me that I ______ stay here until she comes back.
—— Do you mind my opening the window? It’s a bit hot in here. —— ______ , as a matter of fact