The period of the business cycle in which the real GDP is increasing is called the? The period of the business cycle in which the real GDP is increasing is called the?

And no, this is not an homework question. I'm a college student and we starting our exams soon. I'm just going through a lot of questions. Both online and previous year's questions from my school. This is quite confusing. I think it is expansion. Then I saw an article on trough on wikipedia that says it is trough. https://en.wikipedia.org/wiki/Trough_(economics)
 Please explain
The trough is not a period, it is simply the lowest point. The opposite of this is a peak, i.e. the highest point. The answer you are looking for is "Expansion" or "Boom". The period in which GDP is falling is called "Recession" or "Contraction".

Also note that the business cycle is typically not defined using real GDP, but rather nominal GDP.