Answer:
Step-by-step explanation:
It appears that the sentences you've provided have some grammatical errors. Let me help you correct them:
When a gas is heated, it expands.
He's always complaining about the service wherever we go.
Susan will take a statistics course next fall.
You should practice, lest you fail.
Here are the corrections and explanations:
"Expanding" is the correct form of the verb to use in this context.
"Every" is unnecessary in this sentence. The corrected sentence uses "wherever" to indicate the general locations where complaints occur.
"Takes" is changed to "will take" to indicate a future action.
"Practiced" is changed to "practice," and "lest" is used to indicate the purpose or intention of practicing to avoid failure.