读短文，判断正误。
My uncle, aunt and cousin live in Canada. Last summer, they came to visit us. First, they flew from Canada to Guangzhou, then they took a bus to our city. We were all happy. We showed them around the city and they
also went to the City Park. We also went hiking in the mountains together. We were all very happy and they took many pictures. They had a great time!
( ) 1. My uncle and his family live in Guangzhou.
( ) 2. We saw my uncle's family last summer.
( ) 3. They came to Guangzhou by bus.
( ) 4. They went swimming in the park.
( ) 5. They went hiking with us.
=0.5atm，
=1.5atm，外界大气压
=1atm．初温均为27℃，
=30cm，
=16cm，
=8cm．活塞处于静止．忽略一切摩擦．求:
=?