I knew I could count on you!
Smith goes to see his boss in the front office. "Boss," he says: "we're doing some heavy house-cleaning at home tomorrow, and my wife needs me to help with the attic and the garage."
"We're short-handed, Smith." the boss replies. "I can't give you the day off."
"Thanks, boss," says Smith, "I knew I could count on you!" 
我知道你会帮我
史密斯去找他的老板。“老板，我们家明天有很重的工作要做，我妻子让我修阁楼和车库。”
“可我们很缺人，史密斯。”老板答道，“我不可能放你的假。”
“谢谢，老板。”史密斯说，“我就知道你会帮我。”