阅读下面短文，按照句子结构的语法性和上下文连贯的要求，在空格处填入一个适当的词或使用括号中词语的正确形式填空。
One day an elderly  teacher took a walk  through a  forest, with a pupil by his side. Suddenly he      （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      full-sized tree. The tutor  said  to his  young      （company）,“Pull up the first plant.” The boy did so eagerly,      （use）only his fingers．
“Now  pull  up  the  second.” The  youth  obeyed     found  that  the task  was      （difficult）.
“Do the same     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     leaves．“This, my son, is just        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,       we pray and struggle ever so sincerely!”