Final answer:
The correct option is 1. Wall-hung lavatories should be supported by wall brackets, which are the standard method for securing these fixtures due to their ability to support weight and allow for easy maintenance.
Step-by-step explanation:
Wall-hung lavatories, typically found in bathrooms, require appropriate support to ensure stability and safety. The correct answer is that they should be supported by wall brackets.
Wall brackets are the standard method for securing these fixtures to the wall, providing the necessary support to handle the weight and usage of the lavatory. The use of wall brackets also allows for the space beneath the lavatory to remain clear, making for easy cleaning and a more streamlined appearance.