Final answer:
The correct instruction for using vitamin B12 intranasal medication for malabsorption syndrome is to 'Take this medication once per day.' This route of administration bypasses the GI tract, and there is no need for nose massage, hot liquids post-administration, or refrigeration unless stated.
Step-by-step explanation:
The instruction for a client with a new prescription for vitamin B12 intranasal medication to treat malabsorption syndrome should include specific guidance on how to properly use the medication. In this case, the correct answer among the options provided would be 'Take this medication once per day.' This is because the intranasal route allows for the absorption of vitamin B12 directly into the bloodstream, bypassing the gastrointestinal tract where malabsorption issues may prevent proper uptake. Furthermore, clients do not need to massage their nose or drink hot liquids after administration, and the medication should be stored according to the manufacturer's instructions, which typically does not require refrigeration unless specified.