Correct Answer: whistled in the dark

Solution : The correct choice is the first option.

Explanation: Whistling in the dark means to act confidently or remain cheerful in a situation where one is fearful, uncertain, or facing danger. It's akin to putting on a brave face or pretending to be confident despite feeling anxious or uncertain about what lies ahead. In the context of the sentence, despite knowing the dangers ahead, the person tries to keep up their confidence by whistling in the dark.

The meanings of the other options are as follows:

• "Made of sterner stuff" refers to someone being of stronger or tougher material or character.
• "Stepped up his game" means to improve or increase one's efforts or performance.
• "Wouldn't be caught dead" implies that someone would never do something under any circumstances, emphasising strong reluctance or refusal to participate in a particular activity or situation.

Therefore, the correct answer is whistling in the dark.