If there is no government and no foreign trade, then:

The correct option is G = T = M = X = 0.

To understand why this is the correct answer, we can break down the standard macroeconomic variables representing the government sector and the foreign sector in an economy:

1. Government Sector Variables:
- G represents Government Purchases/Expenditures (spending on goods and services by the government).
- T represents Net Taxes (tax revenues collected by the government from households and firms).
If there is no government in the economy, there is no government spending and no taxation. Therefore:
$G=0$
and
$T=0$

2. Foreign Sector (Trade) Variables:
- M represents Imports (goods and services purchased from other nations).
- X represents Exports (goods and services sold to other nations).
If there is no foreign trade, the economy is completely closed to the rest of the world. This means there are no imports coming in and no exports going out. Therefore:
$M=0$
and
$X=0$

Combining all of these conditions together, we find that all four variables must equal zero:
$G=T=M=X=0$