It is false because openin the economy leads to addition of another term in aggregade demnd equation which is exports-imports
now marginal propensity to export depends on the foriengn income which we take to be exogenous and mrginal propensity to import depends on the domestic income.....imports can b considered as a leakage from the system which reduces the multiplier
Akshay Jain
Masters in Economics
Delhi School of Economics
2013-15