这20美元只是杯水车薪。
It can generate 194 megawatts of electric power, but that's just a drop in the bucket.它可以产生194兆瓦的电力,但那只是沧海一粟。
Her 20-dollar donation is a drop in the bucket because they need to raise thousands of dollars for this project.她20美元的捐款只是九牛一毛,因为他们需要为这个项目筹集几千美元。