The reason I think this is the correct option is because firstly a first aider should be gentle so the person doesn't feel that much pain. And they also should be watchful in case something went wrong. And lastly they should be a bit quick.
Glandsome means being cheerful. In my opinion the first aider should be calm so the person their aiding doesn't worry too much. And I don't feel like its necessary for them to be cheerful.
