anamountof与amountof的用法与区别?

Steven planned to carry on a small amountof _________ with his A: commerce B: commercialize C: commercial D: commerced

Steven planned to carry on a small amountof _________ with his friends. A: commerce B: commercialize C: commercial D: commerced

When building a computer with a 32 bit processor， which of the following is the MAXIMUM amountof memory supported？（） A: 1GB B: 2GB C: 4GB D: 8GB