If a mouse of over eight times its normal size has been produced by introducing human growth hormone gene, the technique involved is called

The technique described is genetic engineering, specifically creating a transgenic organism by introducing a foreign gene (human growth hormone) into the mouse genome. Option B (genetic breeding) is the closest among the choices, though it's a somewhat imprecise term. Option A (hybridisation) typically refers to crossing different species or varieties, Option C (mutation breeding) uses radiation or chemicals to induce mutations, and Option D (hormonal feeding) would involve direct hormone administration, not gene transfer.