He can't go out because he has to study for his exam

-He can't go out because he has to study for his exam
=> if
-she is lazy so she can't pass the exam
=>
-he will pay me tonight because i will have enough money to buy a car
=>
-she is very shiy , so she doesn't enjoy the party
=>
-he smokes too much ; that's why he can't get rid of his cough
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