Present perfect

°AFFIRMATIVE:
Subject + have + verb in past participle + complement
(I, we, you, they)

Subject + has + verb in past participle + complement
(she, he, it)



°NEGATIVE:
Subject + have not + verb in past participle + complement
(I, we, you, they)

Subject + has not + verb in past participle + complement
(she, he, it)


°INTERROGATIVE:
Have + subject + verb in past participle + complement + ?
Answer = No, subject + have

Has + subject + verb in past participle + complement + ?
Answer = Yes, subject + hasn´t


*EXAMPLES:
-Spending on food has fallen for many year and continues to drop.
-I´ve studied English for 2 years.
-I´ve studied English since 2006.
-In the last month prices have increased by 12 per cent.
-In the last days, we started a new semester.
-In the last four semesters we have taken Business English.
-How long have you studied English?


*NOTE: For present perfect, we can use this words:
-Recently.
-In recent years.