9 I'm afraid I can't join you for dinner tonight. I'm absolutely under with work at the moment.

The correct answer is D frosted. The sentence implies being overwhelmed or extremely busy with work. While not a standard idiom, 'frosted' in this context could be interpreted as being 'frozen' or stuck due to excessive work, or it might be a typo for 'snowed under', which means to be overwhelmed with work. Given the options, 'frosted' is the most plausible choice if it's intended as a variation or a less common idiom.