Explanation
This question touches upon a couple of issues that relate to hedging foreign exchange exposures using futures contracts. Firstly, many futures contracts on exchanges are available only at specific maturity dates, for example, the IMM dates. They may or may not coincide with actual liabilities for a running business. Also, futures contracts are standardized, ie their notional amounts are fixed rounded sums, and they can only be traded in whole numbers. This often means business using futures for hedging end up having a close enough, but not perfect hedge.
For our importer in the question, clearly he has to buy USDs so he can make his payment. Since each contract gives him USD 100k, he should buy 11 contracts that will get him very close to the amount he finally needs.
Also, the contract expires a month later than his liability is due. This means he should offset the contract by closing it out in August soon as he has made his payment. This will allow him to stay hedged till August. If he does not sell out of the contracts, he will become exposed to a long position for one month till the contract settles, a risk which is unnecessary for him.
Therefore Choice 'b' is the best answer.