Select the correct plural form for the given word: Thief

To form the plural of a word ending in -f or -fe, change the f to v and add -es. If the word ends in -fe, change the f to v and add -s. In both cases, the plural ends in -ves.

For the word 'thief', which ends in -f, change the f to v and add -es to get 'thieves'.

This rule applies to other words like 'leaf' → 'leaves', 'knife' → 'knives', and 'wife' → 'wives'.