Matrix multiplication is not what most people guess on first encounter (multiplying each matching position together, like you would with two vectors). It's a different, specific operation, and getting the rule straight now will save you from a very common bug later: shape mismatch errors, which are probably the single most common error message you'll see across every lab in this entire course track.
1-A 2-A 3-A 4-A | 5 rows 6 A 7 = No - inner dims 2 and 3 differ; transpose one first 8 = Same matrix (identity property) 9 = Every linear/dense layer of a network | 10 = [[1,4],[2,5],[3,6]] - shape (3,2)