"Their defence is the strongest defence that we know of."
Translation:Pertahanan mereka merupakan pertahanan terkuat yang kami tahu.
Halo teman! I think this verb would be optional here. It seems that is just part of the sentences with examples of "me--an verbs", and then the exercise is intended to show its use.
Other versions with zero copula, "adalah", "ialah" ("ialah" is only for third singular person) can be acceptable translations. The zero copula is appropriate in colloquial speech, but it is necessary to avoid the ambiguity between noun phrases in some cases, so the speaker can use a silent stop between the subject and the predicate, while in writing this ambiguity is solved by the use of "adalah", "ialah" as predicative markers (the particle "lah" is indeed indicating the point where the predicate begins), or else, by using the verbs "merupakan" / "menjadi", to form a copular sentence.
Then, the sentence construction would be:
Pertahanan (defense) + mereka (their) + silent stop / adalah / ialah / merupakan (is) + pertahanan (defense) + terkuat (the strongest) + yang (that, used as an agent linker here, and sometimes can be optional) + kami (we) + tahu (know)
Selamat belajar! :)
Terima kasih banyak, Mas. I was really just trying to figure out whether merupakan was a true synonym for adalah or whether it had some more limited use. From what you are saying here, it sounds like it could be substituted in any case and just cause a change in style.