well multiplying matrices is just multiplying first row of first matrix * first column of second matrix and so on, so 2*3 matrix times 2*1 matrix equals 2*3 matrix.
length ×weight =area example:you need to measure a full sheet pan and let's say if it is 8 full sheet pan you weighs 23 so you want to multiply 8×23=184 that is your area okay 2×3=6 and 2×1=2 so to figure out the area multiply 6×2=12 so the answer is matrix B just remember length times weight equal areas
