根据句意，用所给单词的适当形式填空。
Can you guess the _______ of the tree? (high)
Millie keeps writing in English about her _____life. (day)
Nowadays I can choose online courses and study by_____. ( I )
The old granny fell on the street, but ______, some students offered help to her.(lucky)
Believe yourself. Nothing is ________if you put your heart into it. (possible)