( left[ begin{array}{c c c r r r r}2 & -1 & 6 & 3 0 & 14 & 8 & 0 0 & 0 & 5 & 1 0 & 0 & 0 & 3 end{array} right] ) is a _____

• A. Principle diagonal matrix
• B. Upper triangular matrix
• C. Lower triangular matrix
• D. Singular matrix