Expectorants are indicated in the presence of which type of cough?

The correct answer is that expectorants are indicated in the presence of a productive cough. Expectorants work by increasing the production of mucus in the airways and helping to loosen and clear congestion in the lungs. This is particularly beneficial in cases where there is thick or excessive mucus associated with respiratory infections, bronchitis, or other conditions that produce a productive cough.

In contrast, a dry cough, or non-productive cough, does not involve mucus and typically does not require an expectorant. Such coughs may be caused by irritation or inflammation in the throat or airway, and therefore, treating them with an agent that promotes mucus production may not be appropriate. The term "recurrent" doesn't address the nature of the cough and is more related to the frequency rather than its productive quality. Thus, expectorants are specifically geared toward alleviating symptoms associated with productive coughing, making this the most suitable option.