First of all we dont know what authors your talking about how are we supposed to help..?
Even though there are not any underlined words, it is clear that Gregor feels relief.
Gregor was relieved that he wasn't chosen last. Gregor <u>exaled deeply</u> because he could finally relax. The author even notes that his posture <u>relaxed</u>. His muscles no longer felt tense. His heartbeat <u>steadied</u>, which means he was no longer worried or stressed.
I think it is D
Hope this help you?! Hope