You solve a non$-$singular system of $1,000$ linear equations with $1,000$ unknowns. Your code uses the Gauss$-$Jordan

algorithm with partial pivoting using double precision numbers and arithmetics. Why would the one$-$norm of the

residual of your solution not be equal to zero? $($mark all correct answers$)$

a$)$ a zero is encountered in the pivot position;

b$)$ truncation errors;

c$)$ round$-$off errors.