For a second Rudolf thought his host [the lighthouse keeper] might be joking； but the serenity o f 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】：原句意为：片刻之间鲁道夫以为主人在跟他开玩笑.但他那认真的表情告诉他这不是玩笑。A项意为"……但是鲁道夫从老人的表情中看出，他并不严肃"；B项意为“……但是鲁道夫的表情告诉老人，他不只是在开玩笑”；C项意为“……但是老人平静的表情让鲁道夫确信，他并没有开玩笑”；D项意为“……但是鲁道夫看上去很平静，因此老人確信他是认真的”。答案为C。
