If you are unsure of the correct form, check a dictionary. The attorney won her case. The attorneys won their cases. The company is improving its service. The companies are improving their service.
Adverbs are words that describe verbs, adjectives, or other adverbs.
Make sure that you use the adjective form of a word when the word describes a noun and the adverb form when it describes a verb, adjective, or other adverb. If you are unsure of the correct form, check a dictionary. Symphony 39, for example, opens in an exciting way. The activist, a woman with impeccable credentials, has changed legislators' minds about a number of issues. The White House, which is in Washington, is a national treasure.