When gross investment becomes zero, which of the following prevents national income from becoming zero?

The correct answer is A. Consumption.

Consumption is the largest component of GDP, accounting for about 60% of total output. When gross investment

becomes zero, consumption will still continue, which will prevent national income from becoming zero.

The multiplier is a measure of the effect of a change in investment on national income. The accelerator

is a measure of the effect of a change in national income on investment. Both the multiplier and the accelerator are important concepts in macroeconomics, but they do not prevent national income from becoming zero when gross investment becomes zero.

In conclusion, the correct answer is A. Consumption.