Question

what does a trough indicate?

the gdp has stopped increasing and has begun to decline.

the gdp is stagnant.

there is a gdp gap.

the gdp has stopped declining and has begun to increase.

Explanation:

In economic cycles, a trough is the lowest point where a period of GDP decline (recession) ends and a period of GDP growth (expansion) starts. This matches the description of GDP stopping its decline and beginning to rise.

Answer:

The GDP has stopped declining and has begun to increase.