In FEM, the forced vibrations equation after Finite Element discretization of a structure can be expressed as which option?

(a) Mẍ+Kẋ=F

(b) Mẍ+Kẋ=0

(c) Mẍ+Kx=F

(d) Mẍ+Kx=0

The question was posed to me during an internship interview.

My enquiry is from Eigen Value and Time Dependent Problems topic in chapter Single Variable Problems of Finite Element Method