Labelling is an element of which 'P' of marketing mix?

Product

The correct answer is Option (1) - Product.

A simple looking but important task in the marketing of goods relates to designing the label to be put on the package. The label may vary from a simple tag attached to the product (such as in case of local unbranded products like sugar, wheat, pulses, etc.) indicating some information about the quality or price, to complex graphics that are part of the package, like the ones on branded products. Labels are useful in providing detailed information about the product, its contents, method of use, etc. It is an important function of labeling to provide information required by law. For example, packaged food articles must have list of ingredients declaration regarding vegetarian or non-vegetarian food additives and date of manufacturing or packing on the label. Such information is required on processed foods, drugs and tobacco products. In case of hazardous or poisonous material, appropriate safety-warning need to be put on the label.