I know that when market value of inventory is greater than cost, the inventory account is credited and there is a loss for decline in the market.
First, I guess we're making the assumption that prior to this point in time it was already listed at market and had to be reduced to cost. The problem is not specific about that (unless there's missing information). If it was already at cost prior to this point in time, then it would simply stay at cost and nothing would change.
Also there is a reduction in income so I believe that either 1 or 3 is the answer. However I am having trouble understanding how the current ratio (assets/liabilites) will play a role since those numbers can vary item by item.
You don't need to know individual items. Current ratio contains total current assets. Inventory is a current asset, so the total goes down. What would that do to the current ratio? (This is based on the assumption we're changing from market back to cost.)