21 ------ He runs his own company at the age of 21. ------- ___________________
When you read the book, you' d better make a mark _____ you have any questions.
We'd better hurry ______ it is getting dark.
I didn' t manage to do it _____ you had explained how.
_____ he comes, we won't be able to go.
I hurried _____ I wouldn't be late for class.