Explanation:

- Treatment for childhood cancer is challenging but children are very ___________ and recover quite soon.

• Option 1: Resilient - This means being able to withstand or recover quickly from difficult conditions. It fits well here, emphasizing children's ability to bounce back after challenging treatments.

• Option 2: Resiling - This word means to draw back or retreat. It's not commonly used in this context, making it less suitable.

• Option 3: Decrepit - This refers to being old or feeble, the opposite of how children are often seen in this context.

• Option 4: Frail - This implies weakness and fragility, opposite to the intended meaning of strength and recovery.

• Option 5: Plaintive - Meaning sounding sad and mournful, not relevant here.