听短文，选择正确的答案
16． How can we eat a balanced diet？
A． Eat some fruit and vegetables．
B． Only eat fruit and vegetables．
C． Eat no meat．
17． What helps us build a strong body？
A． Eating much．
B． Doing exercise．
C． Talking and laughing．
18． Why should we have many friends？
A． Because we can be happy．
B． Because we can talk and laugh with them．
C． Because we can relax ourselves．
19． What do the studies show？
A． People with many friends get sick easily．
B． People with no friends won't get sick．
C． People with many friends get less sick．
20． How many ways according to the passage can help keep healthy？
A． Two．
B． Three．
C． Four．