Choose the missing terms out of the given alternatives : PMT, OOS, NQR, MSQ, ?

The correct answer is LUP.

PMT, OOS, NQR, MSQ, LUP are all acronyms for mathematical terms.

PMT stands for Present Value of Money.
OOS stands for Out of Service.
NQR stands for Non-Quadratic Residue.
MSQ stands for Mean Squared Error.
LUP stands for Lower Triangular Upper Triangular Cholesky Decomposition.

The LUP decomposition is a way of writing a matrix as a product of a lower triangular matrix and an upper triangular matrix. It is a useful tool for solving systems of linear equations and for finding eigenvalues and eigenvectors of matrices.

The other options are not acronyms for mathematical terms.