下列各组中的两种物质作用时,反应条件(温度、反应物用量等)改变,不会引起产物改变的是 ( )
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 _______ .
My friend showed me round the town, ______ was very kind of him.