Regioselective enolate formation, choosing major and minor products
A major factor contributing to the stability of the enolate ion formed as the major product (F) is the stability associated with extended conjugation or extended delocalisation via resonance. Due to this, terming (F) as the major product seems justified.
If the product were to be a kinetically-controlled one (KCP), then the presence of three acidic alpha hydrogen atoms could've caused faster formation of product (E) ; it still would not have been the more stable product, but since the major product in KCP-type reactions is controlled more by the kinetics , rather than the thermodynamics, we would possibly expect to see (E) in a larger yield in that case.
Note: Strictly speaking, the problem should mention conditions that can help us to unambiguously determine which pathway (KCP vs. TCP) should be chosen. But a practical advice, garnered from the experience of working problems which seldom perfectly mention the reaction conditions, is that unless mentioned otherwise, it is always wise to first consider the thermodynamically stable product.