CONDITIONAL SENTENCES
Zero Conditional If + Present simple,
Present simple
Example: If you heat water to 100째 C, it boils.
First Conditional If + Present simple,
Future Simple
Example: If Bill studies, he will pass the exam
Second Conditional If + Past simple,
Would/could + infinitive
Example: If I won the lottery, I would travel around the world.
Third Conditional If + Past perfect, (had + past participle)
Would/could have + past participle
Example: If If Suzanne had gone on a diet as her doctor recommended, she wouldn't have had the heart attack.
Try this exercise! http://www.e-grammar.org/if-clauses/test1-exercise1/