The answer is: C
Explanation
According to the doctrine of res judicata, a matter that has been finally decided by a competent court cannot be litigated again between the same parties. However, there are some exceptions to this rule, where res judicata does not apply.
One of the exceptions is dismissal in default. This means that if a suit is dismissed for non-appearance of the plaintiff, or for non-payment of court fees, or for failure to take any necessary step, the plaintiff can file a fresh suit on the same cause of action. This is because such a dismissal does not amount to a decision on the merits of the case, and therefore does not bar the subsequent suit.
Another exception is consent/compromise decree. This means that if a suit is decided by a compromise between the parties, the compromise does not operate as res judicata for any matter that was not directly and substantially in issue in the suit. This is because a compromise is based on the agreement of the parties, not on the adjudication of the court, and therefore does not bind the parties beyond the terms of the compromise.
Therefore, the correct option is C: both (a) & (b). Res judicata does not apply in cases of consent/compromise decree and dismissal in default.