When Nike branched out from selling only athletic shoes to also offering athletic clothing and gym bags, what type of growth strategy did this represent?

The growth strategy represented in this scenario is indeed product development. This strategy involves a company enhancing its product offerings by introducing new products that are related to its existing line. When Nike expanded from solely selling athletic shoes to also including athletic clothing and gym bags, it effectively sought to meet the needs of its existing customers more comprehensively.

Product development typically focuses on innovating or creating new items that complement the current product range, leveraging existing brand equity, and aiming to increase sales from the current market segment. Nike's decision to offer clothing and gym bags complements its primary product line of shoes and caters to the same target audience of athletes and fitness enthusiasts. This move aligns with their established brand identity and allows them to offer a more comprehensive athletic experience to consumers.

Market penetration, market development, and diversification represent strategies that involve either increasing market share with existing products, targeting new markets with existing products, or venturing into entirely new markets with new products, respectively. These do not accurately describe Nike's strategic move of adding related products within their existing market.