Complete the sentence -
If they had started earlier, _____________.

• If- যুক্ত clause টি past perfect tense এর হলে principal clause টি perfect conditional হয়। 
- এক্ষেত্রে structure হয়: Subject + would have/could have/might have + verb এর past participle. 

Complete sentence টি হবে - If they had started earlier, they could have got the train.

Source: Advanced Learner's English Grammar & Composition by Chowdhury & Hossain.