If the systematic VaR for an equity portfolio is $100 and the specific VaR is...

Choice 'd' is correct because VaR is sub-additive in cases where correlation is less than one.

Specific VaR refers to the risk in the portfolio from security selection, ie the risk from holding the specific equities in the portfolio, while systematic risk refers to the market risk. Definitionally, specific risk and systematic risk are uncorrelated, ie their correlation is zero. Since their correlation is zero, combining them will produce a VaR number lower than their stand alone aggregate. Total risk includes both specific risk and systematic risk, and can be calculated taking into account the specific and systematic VaRs and their correlation.

All other answers are therefore incorrect.