The high-pressure engine was ________lighter in proportion to horsepower, and with less than half as many moving parts was much easier and cheaper to repair.
句意：高压发动机重量与马力的比例明显比发动机好，而且运动部件的数量还不到发动机的一半，修理起来就容易得多，也便宜得多。far在这里是程度副词，用于修饰比较级。因此，本题的正确答案为C。