Step 1: Recall what a tariff does.
A tariff is simply a tax the government adds onto goods coming in from other countries, which makes those foreign goods more expensive in the local market.
Step 2: Think about why a government would want that.
If cheap imports are allowed to flood in freely, local businesses making similar goods can lose customers and shut down, so raising the price of imports through a tariff gives local producers a fair chance to compete.
Step 3: Rule out the other options.
A tariff clearly restricts rather than supports free trade, and it raises rather than lowers the cost of imports, and it has nothing to do with cutting paperwork or attracting investment directly.
Step 4: State the final answer.
So the real purpose of a tariff here is protecting local industries. Hence, the correct answer is option (B).