1. Do you think our missionaries will be able to convert everyone in their areas.
In this sentence, convert is used as a verb (B). A verb is a word that shows action. In this case, the missionaries are trying to change the ideas of everyone to their areas. When convert is used as a verb, the accent is placed on "vert" (D).
2. Do not subject anyone to ridicule.
In this sentence, subject is used as a verb (B). Again, a verb is a word that shows action. If it would be used as a noun, it would be talking about a school subject or a specific theme. This is not the case in this sentence. When subject is used as a verb, the accent is placed on "ject" (D).
3. I expect an increase in salary next month.
In this sentence, increase is used as a noun (A). When increase is used as a noun, it means an instance of growing or making greater. In this case, the salary is bigger. When it is used a verb, it means become or make greater. While these definitions are similar, in this sentence it is used as a noun. When increase is used as a noun, the accent is placed on "in" (C).
4. No protest was expected over the decision of the judge.
In this sentence, protest is used as a noun (A). In this case, they are talking about a protest, perhaps where people stand outside with signs. They are not referring to the act of protesting. When protest is used as a noun, the accent is placed on "pro" (C).
One good way to know which syllable the accent is placed is to say the word out loud.