在 the/your,etc ability to do sth.这个搭配中, ability 只用单数。例如:
The system has the ability to run more than one program at the same time.
该系统能够同时运行一个以上的程序。
Everyone has the right to good medical care regardless of their ability to pay. 无论支付能力任何,每个人都有权得到良好的医疗保健。
A gentle form of exercise will increase your ability to relax.
和缓的运动锻炼会提高自我放松的能力。
(以上摘自《牛津高阶英汉双解词典》第9版,p.3)