Here are the correct answers to your multiple-choice questions:
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For "Term cosas (indefinite)" the correct answer is unas. (Indefinite articles can be "un" for masculine singular, "una" for feminine singular, "unos" for masculine plural, and "unas" for feminine plural.)
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For "Term some pencils" the correct answer is unos lápices. (Lápices is masculine plural, so the indefinite article "unos" is appropriate.)
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For "Most nouns that end in -ma are..." the correct answer is masculine. (In Spanish, most nouns that end in -ma are indeed masculine.)
If you have further questions or need more assistance, feel free to ask!