The connection between modern, old, and weak is like a comparison you might find on a standardised test. The order is “modern: antiquated: weak:,” which means “Modern is to antiquated as weak is to.” After that, there are some word choices for the student to look at.
Strong, firm, powerful, sure, unbreakable, able, and healthy are all good answers. Students know that modern and old are opposites, so words that make sense to use with the word “weak” have the opposite meaning.
On standardised tests, students can choose one of four ways to finish the analogy. This kind of question shows up on tests for “verbal comprehension” or “language.”