I need more explanation on correct answer. Thank you.

1. Which is the key assertion being addressed by the following internal control for sales: all sales invoices are supported by authorised goods outward dockets (ie delivery dockets) and approved customer orders?

A.Existence

B.Occurrence

C.Accuracy

D.Completeness

2. Which is the key assertion being addressed by the following internal control for Purchases : the office manager ensures purchase orders are filed in numerical sequence and the sequences are periodically?

A.Existence

B.Completeness

C.Cut-off

D.Accuracy