他们的错误能够被改正。

[误] Their mistakes are able to be corrected.

[正] Their mistakes are capable of being corrected.

注：be able to 的主语一般是物，表示某人有做某事的能力。capable 的主语可以是人，也可以是物，表示有达到一般要求的能力。本句主语是 mistakes，故须用 capable。