All the stars in this photo are at about the same distance from Earth (some 25,000 light-years away). Which stars in this picture are the largest in size (radius)?

You did not add the photo, but the bright red stars are the largest in size (radius).

Explanation:

Red stars are giant, luminous stars. They are the stars with the largest size (radius) among all the other stars and usually have very low temperatures (below 500k). The brighter these stars appear to human eyes, the greater their actual size.

Red stars have rays hundreds of times larger than the sun, literally being the biggest stars in space. Despite their gigantic size, these stars have low density.

you'd use the equation that establishes a relationship between  energy  and  wavelength, which looks like this

e=h⋅cλ, where

λ  - the wavelength of the photon; c  - the speed of light, usually given as  3⋅108m/s; h  -  planck's constant, equal to  6.626⋅10−34j s

plug the value you were given for the energy of the photon in the above equation to get the wavelength

e=h⋅cλ⇒λ=h⋅ce

λ=6.626⋅10−34js⋅3⋅108ms−1.257⋅10−24j=1.581⋅10−1m