【广东省2015年中考英语试题】---- Sir, Jenny wants to know when she can leave the office. ----- Only when she ______ copying this report.
We are wondering ________ we can prevent people from polluting the earth.
The gravity on Mars is only about ________ of that on Earth.
It is hard to imagine what life __________ in 100 years.
My friend John insisted that he had seen ______ alien the day before.
--- What pleasant weather! Shall we go boating on the lake? --- _______.