The correct answer is: (1) and (2) only.

An increase in price sensitivity is likely to reduce sales of a differentiated product as customers migrate to the cost leader's (probably) cheaper offering.

Marketing communication is fundamental to a strategy of differentiation, since prospective customers must appreciate why the product is different if they are to become motivated to buy it.

The cost leader is selling to its own market segment and is unlikely to be concerned with the market for the differentiated product.

A unique feature protected by patent will make differentiation more effective as a marketing tool, since competitors will be unable to copy it.