Learn Hardcore Japanese: sensei ha nihongo no mondai wo setumeisimasu.

The particle は marks 先生 as the topic of the sentence. It tells us that we are talking about “the teacher” and sets up what we’re going to say about them.

Why isn’t 先生 marked with が instead?

Using が would mark 先生 as the subject in a neutral or new-information sense. Here, 先生 is already known or introduced, so は is more natural for topic-comment sentences like this one.

How does の work in 日本語の問題?

The particle の links 日本語 (Japanese language) and 問題 (questions/problems), showing that the problems are related to or about Japanese. It functions like the English “of” or the possessive ’s in “problems of Japanese.”

What role does を play before 説明します?

The particle を marks 日本語の問題 as the direct object—the thing that is being explained by the teacher.

Where is the verb, and what form is it in?

The verb is 説明します at the end. It’s the polite present (non-past) form of 説明する (“to explain”), meaning “(will) explain” or “explains.”

Can 説明します refer to future action?

Yes. In Japanese, the polite non-past 説明します can mean either present (“explains”) or future (“will explain”). Context tells you which one is intended.

How do you pronounce 説明します, and what’s its romanization?

It’s pronounced [se.tsu.meː.ɕi.ma.sɯᵝ] and romanized as setsumei shimasu.