An elderly teacher，with a pupil by his side，took a walk through a forest. Suddenly he__41__(stop)and pointed to four plants close at hand. The first was just beginning to appear slowly above the ground，the second had rooted itself pretty well into the earth，the third was a small short tree，while the fourth was__42__ full-sized tree. The tutor said to his young__43__(company)，“Pull up the first plant. ” The boy [KS5UKS5U]did so eagerly，__44__(use)only his fingers.
“Now pull up the second.” The youth obeyed__45__ found that the task was__46__(difficult)．[KS5UKS5U]
“Do the same__47__ the third，” he urged. The boy had to use all his strength to uproot it.
“Now，” said the instructor，“try your hand with the fourth. ” The pupil put his arms around the trunk of the tall tree and couldn't even shake__48__ leaves. “This，my son，is just__49__ happens with our bad habits. When they are young，we can remove them easily；but when they are old，it's hard to pull them out of the ground，__50__ we pray and struggle ever so sincerely！”