Answer:
A & D
Step-by-step explanation:
A) Forgetting to attach a document/misclicking is a common issue when sending documents.
B) Attaching a document is not a complex topic and does not require much time.
C) There are other ways of attaching a document; after looking, it is not hard to find the icon. You can also search for the file uploader button as well.
D) This is a big issue; to scale the document down, you have to shrink it or transform the size. It creates multiple issues.