Choose the closest paraphrased version after the following sentence or the italicized part.
For a second Rudolf thought his host [the lighthouse keeper] might be joking; but the serenity of the other’s expression reassured him.
A、
... but Rudolf found from the old man’s expression that he was not serious.
B、
... but Rudolf’s expression showed the old man that he was only joking.
C、
... but the old man’s calm expression convinced Rudolf that he was not joking.
D、
... but Rudolf looked peaceful, so the old man was sure that he meant what he said.
【正确答案】：C
【题目解析】：
句意：有那么一刻，鲁道夫认为他的主人（灯塔管理员）可能是在开玩笑；不过他那认真的表情使鲁道夫确信那不是开玩笑。