Questions & Answers about Czy to są twoje klucze?
Why do we use to for "these" instead of a plural word like te?
When pointing things out with the verb "to be", Polish uses the fixed phrases to jest for singular ("this is") and to są for plural ("these are"). Even though klucze (keys) is plural, the pointing word to never changes in this specific construction!
Why does the plural word klucze end in -e? I thought masculine nouns usually take -y or -i.
You are right that many masculine inanimate nouns take -y or -i (like telefon becoming telefony). However, nouns that end in certain "soft" or "historically soft" sounds—like the -cz sound in klucz—take the ending -e in the plural instead.
Why is the word for "your" twoje here?
Because klucze is plural, the word for "your" has to be plural to match it. Polish has two plural categories: one for groups with at least one male person (virile) and one for everything else (non-virile). Since keys are just objects, we use the non-virile plural form twoje.
Do I have to start this sentence with Czy?