Without air protection, the sun's rays______. A: will become very cold B: will do good to human beings C: will become hot D: will do harm to human beings

1. How did human being become effective hunters? A: Human body is especially adapted to be good hunters. B: Human beings were biological superior that helped us to become effective hunters. C: Human beings were born with a bigger brain and became effective hunters. D: Human beings were able to domesticate animals to become effective hunters. E: Human beings were physically weak and we had to develop tools to become effective hunters.

Global Warming Global warming A mix of ______________ and irregular climate change Cause of global warming ________________: carbon dioxide, water vapor, and methane ________________: using forests as fuel, for building, furniture, etc. The use of __________________ on crops _____________________ Effects of global warming Destruction of important _______________________ systems Loss and endangement of many ___________________________ _______________________________________ Solutions to global warming To reduce gases put into atmosphere Be more _______________, use wind and solar power etc. To in crease greenhouse gases taken out of the atmosphere Planting trees Making changes to the _____________________________

In summary, the humanities help to create well-rounded human beings with insight and understanding of the passions, hopes and dreams common to all humanity.

Global warming is caused by human activities except the greenhouse effect.（ ）