Answer:
(a) Stem cells: unspecialised cells which can divide repeatedly and can develop into different types of specialised cells. They are found in the embryo, in bone marrow, in cord blood and in some adult tissues, and are used to treat diseases such as leukaemia and to grow new tissues.
(b) Cloning: the production of an exact genetic copy of a cell, a tissue or a whole organism from a single cell or nucleus. The nucleus of a body cell is put into an egg cell whose nucleus has been removed, and the egg is grown to an embryo. Dolly the sheep was the first mammal cloned this way.
(c) Genetically modified crops: crops whose genetic material has been changed by biotechnology to give them a new useful character. For example, Bt cotton carries a gene of Bacillus thuringiensis which makes it resistant to bollworm, and golden rice is rich in vitamin A.