cook

The question you wrote has one error and several test points:
1. "have持续65 years"==> has --> one error
testing points:
1. "which" ,I guess ,herein, refers to the whole thing which " The design of the US dollars have持续65 years",-->  so, maybe the answer is " , making ...."
2. the differce between " easily and easy"
3. "it"--> could be right if it refers to " forged of all currency"
4. I guess the answer: " making it more easily and frequently to forge all currency" or " making it more easily and frequently forged currency)?  
I am not sure about answer 2. forged of currency ??? --> should be forged currency or forge of currency .

Are you sure the options you offered is correct?

cook

ok, I will try " making it more easily and frequently to forge of all currency".

cook

To vin0410: Those are different. You mixed up.