When investigating the pH (acidic, neutral, alkaline) of a liquid, don't soak the litmus paper completely in the liquid but just put the end of the paper in it.

The mirror on a compact I got from a friend has cracked.

However, the preposition+relative pronoun (which) part becomes a relative adverb (where).

Rust is gradually eating into the metal parts.

Well that's because in fiction that sort of fine detail gets skipped.

Now that you mention it, I wasn't involved in the decision-making for the vital part.

The "predicate" is that part that shows the action in the sentence. In Japanese it would be the part that ends in "da", "suru", etc.

The "subject" is the person or object to carry out the action in the sentence. Transformed to Japanese it would be the part that end in "wa" or "ga".

Work is a very important part of life in the United States.

Land occupies the minor portion of the earth's surface.