SAT - Writing & Language - Grammatical Construction
The meaning of both the phrases is the same. Healthy is an adjective while healthily is an adverb. One will hear the words 'eating healthy' used more often than 'eating healthily'. Grammatically it is correct to say 'eating healthily' but many people and authors use 'eating healthy'. It's a matter of choice to use either, as both the words convey the same meaning. And off late healthy has been used as an adverb too.
Both the words us and we are personal pronouns. Pronouns are words that take place of a noun. Both the pronouns we and us are used to refer to more than one person. The pronoun 'we' is used as a subject of a sentence, or to rename the subject of the sentence. eg. We all are going out for lunch today. The pronoun 'us' is used as a direct object, an indirect object and the object of a preposition. eg. Can you please bring us some lunch.
This and that come under the category of demonstrative pronoun. Demonstrative pronouns are pronouns that point to specific things. An easy way to remember when to use this and when to use that is through the principle of distance. If an object of reference is in your sight, you must use this. Eg. This is my friend Heena. If an object of reference is away from your sight you must use that. Eg. That trip we made to Goa was amazing. This and that are also used as demonstrative adjectives when they modify nouns or pronouns. The principle for usage remains the same as the principle of distance. Eg. This apple is spoilt. I did not enjoy reading that book. The words this and that occur right before the noun/pronoun that they modify.