Hurry up! We have to go - five minutes.

A. by

B. in

উত্তর in

ব্যাখ্যা :

point of time (নির্দিষ্ট মুহূর্ত, অগণনাযোগ্য সময়) এর ক্ষেত্রে by হয়।

We have to go by 5 p.m./a.m./o'clock.

I will be back by five o'clock.

I have to finish it by Friday.

I will see by 21 instant.

কিন্তু period of time (গণনাযোগ্য সময়) এর ক্ষেত্রে in হয়।

Hurry! The train leaves in five minutes.

Hurry up! We have to go in five minutes.

The film will start in fifteen minutes.

I will be back in an hour.

I will finish the job in two days/weeks/months.

Needing or using no more than a particular amount of time অথবা,

How long does it take to do sth অর্থে past & future উভয় ক্ষেত্রেই in হয়।

He learnt to drive in ten days.

I did it in one and a half hour.

I will do it in five minutes.

I will have you speaking English in seven days.

তবে past period of time এর ক্ষেত্রে

after হয়। He returned home after a week.

Hurry up! We have to go in five minutes হবে। (by নয়)

রেফারেন্স : Essential English Grammar- Raymond Murphy (Cambridge University Press)

Unit 96 page 200

Hurry! The train leaves in five minutes.

এছাড়া Oxford/Cambridge Advanced Learner's Dictionary তে in ও by দেখুন বুঝতে পারবেন। 

Source: Master Jahangir Alam