A regular checking account simply lets you do all the things you'd expect from a checking account.

Although jellyfish stings occasionally kill humans, some jellyfish can actually benefit people.
Independent clause: some jellyfish can actually benefit people.
Dependent clause: Although jellyfish stings occasionally kill humans

Scientists have used drugs made from jellyfish to treat cancer and heart disease.
Complete verb: Have used
Helping verb: Have

Lifting bags of groceries. - is an example of muscular strength.

The movement of another swimming creature causes the stinging cells in the tentacles of a jellyfish to fire. -prepositional phrase

Medical research may find more uses for jellyfish in the future. - Linking verb

Irregular verbs, prepositional phrases, dependent clauses, compound subjects, and indefinite pronouns are not inherently bad in writing. They are essential elements of language that add variety, clarity, and complexity when used correctly.

Irregular verbs, prepositional phrases, dependent clauses, compound subjects, and indefinite pronouns are not inherently bad in writing; they serve important functions and contribute to the richness of expression. Proper understanding and usage are necessary for effective writing.