The children on the baseball team. is that a complete sentence

No it is not a complete sentence. You are missing another clause - that is a simple clause not a sentence:)

You need something further on, or a connective or time connective before the subject ... "The children".

Hope I helped:)

jewish people, gypsies, and political opponents.

the correct answer is:

true

i am an online student and after i submit my quizzes, it gives me the correct answers to any that i may have missed. the answer to this question is true