在80 g密度为d g·cm-3的硫酸铁溶液中,含有2.8 g Fe3+,则此溶液中SO的物质的量浓度为(单位为mol·L-1)
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
It’s high time you had your hair cut ; it’s getting _______ .