根据问句选答句。
How old are you?____ A. I'm 10.
Happy birthday!____ B. Five.
How are you?____ C. Thank you.
How many boxes?____ D. I'm fine, thank you.
I have a ruler.____ E. Me, too.
下列破坏生态系统稳定性的例子中,属于自然因素的是( )
Who's ___boy in red, do you know?