The correct answer is:
a. foreigners to buy more U.S. assets, which reduces U.S. net capital outflow.
When the U.S. real interest rate decreases, it typically makes U.S. assets less attractive to foreign investors. However, if we are considering the options provided, a decrease in the real interest rate may lead to foreigners finding U.S. assets less attractive (which could contradict the first part of choice 'a'), however, overall, this situation tends to lead to increased capital outflows from the U.S. as Americans seek better returns abroad (left generally in choice 'b').
But with those elements considered, if the first part stands that it reduces net capital outflow properly indicates a decrease in competition for currency and could mean less capital flowing out as returns compare favorably with different assets, there serves a degree of sympathetic reason in 'a' based on the generalization the net capital outflow is a balance of these movements.
Options 'b' and 'c' would clarify that Americans increasing asset purchases abroad correspond to greater U.S. net capital outflow, while reducing outs made but you want to weigh and evaluate the latest dynamics correlated with demand pull slope for asset management in the analysis provided.
If we assert just the overall changes could mean the local losing purchasing such that more of the capital being pushed towards cheaper returns fade away from something agreeable overseas, you might subtly consider balance handled overall as mentioned giving hold under specific fiscal responsibility dynamics brought by relative shifts.