Ringed seals give birth in lairs carved out of packed snowdrifts. Which abiotic change may increase pup mortality?

reduced snowfall
reduced temperatures
reduced polar bear population
reduced carbon dioxide

Reduced snowfall may increase pup mortality because ringed seals rely on packed snowdrifts to carve out their lairs for giving birth. If there is less snow available, it may be more difficult for the seals to create suitable birthing habitat, increasing the risk of exposure to harsh weather conditions and predation.

so which one

Reduced snowfall is the abiotic change that may increase pup mortality in ringed seals.