I did not passed the exam (regret)

• I should study

• I should have studied more

• i must have studied moreI

For a past recommendation we use:

• have + must + past participle

• should or could + have + past participle

• Must or might + have + past participle

For a past suspicion/deduction we use:

• must or might + have + past participle

• should or could + have + past participle

• should + simple present

Gina ate too much and now she has a stomachache

• Gina might not have eaten less

• Gina must have eaten less

• Gina should have eaten less

My friend was arrested last night (suspicion)

• The police must make an error

• The police must have made an error

• The police should have made an error

Karla did not come on vacation with us and now she is sad. ( regret)

• She should have come

• she must have come

• she could come

Past participle of verb come

• come

• came

• comed

Past participle of verb buy

• bought

• buys

• buying

Past participle of verb eat

• eat

• ate

• eaten

I did not study medicine and now I regret it.

• I should have studied medicine

• I must have studied medicine

• I study medicine