Comprehensive and Detailed Explanation:

Option A is true: In emergencies, verbal notices are permitted with the requirement to follow up in writing.

Option D is true: Notices and communications may be sent in various formats including handwritten, typed, printed, or electronic systems.

Option B is incorrect; a notice does not necessarily have to be signed by all these representatives; it depends on the party issuing the notice.

Option C is incorrect; proof of receipt is ideal but not always strictly required for legal validity depending on contract provisions.