Why does sepulchra end in a?
Sepulchrum, sepulchri is a word of the second declension NEUTRAL. Plural for nominative, vocative and accusative is made with "-a".
If you hover over 'are there', you get only 'suntne', which is not offered by the word bank. The correct answer is 'sunt', which is NOT in the drop down. Please fix either the word bank and correct answer; or the drop down.
Don't ask them to fix it here: just report it with "the dictionary hints are wrong or missing", in the report button.
As a rule, do not rely on the hints, they cannot understand the sentences.