My fifth time asking this, but can someone me with these

Pls pls pls pls ! describe, in your own words, how you found the epicenter of the earthquake.

In a simplified model of the human eye, the aqueous and vitreous humors and the lens all have a refractive index of 1.40, and all the refraction occurs at the cornea, whose vertex is 2.60 cm from the retina. what should be the radius of curvature of the cornea such that the image of an object 40.0 cm from the cornea’s vertex is focused on the retina?

Which compound is held together by the electrostatic force between two ions? a. co2 b. cci4 c. h2s d. mgf2