The provision of the Currency Act that is relevant to your question is that colonists were not allowed to issue their own paper currency and had to conduct trade primarily in British currency, gold, and silver. Therefore, the statement "Foreign trade had to be conducted in gold and silver" aligns closest with the provisions of the Currency Act.
The other options you've provided do not accurately reflect the main provisions of the Currency Act as it primarily restricted the use of paper money and regulated currency practices in the colonies.