The correct option is C constrict
The word 'dilate' refers to making o become wider, larger or more open.
Option A, squeeze refers to firmly press something.
Option B, swell refers to becoming greater in number, amount or volume.
Option C, constrict refers to making narrower.
Option D, shorten refers to making or becoming shorter.
Thus, according to the meaning, the word 'constrict' is the opposite of the word 'dilate'.