The plural form of ‘stimulus’ is (a)   .

The plural form of ‘crisis’ is (a)   .

The plural form of ‘thesis’ is (a)   .

The plural form of ‘ox’ is (a)   .

The plural form of ‘datum’ is (a)   .

The plural form of ‘medium’ is (a)   .

The plural form of ‘deer’ is (a)   .

The plural form of ‘tooth’ is (a)   .

The plural form of ‘mouse’ is (a)   .

The plural form of ‘fly’ is (a)   .

The plural form of ‘sheep’ is (a)   .

The plural form of ‘pony’ is (a)   .

The plural form of ‘tomato’ is (a)   .

The plural form of ‘bush‘ is (a)   .

The plural form of ‘lady‘ is (a)   .

The plural form of ‘knife‘ is (a)   .

The plural form of ‘studio‘ is (a)   .

The plural form of ‘hero‘ is (a)   .

The plural form of ‘goose‘ is (a)   .