Endoderm forms

The correct answer is D. viscera and digestive system.

The endoderm is the innermost layer of the embryo, and it gives rise to the lining of the digestive tract, respiratory tract, bladder, and urethra. It also forms the liver, pancreas, and thyroid gland.

The blood and bone are formed from the mesoderm, while the nervous system is formed from the ectoderm.

Here is a more detailed explanation of each option:

• Option A: Blood and bone are formed from the mesoderm. The mesoderm is the middle layer of the embryo, and it gives rise to the skeletal system, muscles, connective tissue, blood, and gonads.
• Option B: The respiratory system is formed from the endoderm. The endoderm is the innermost layer of the embryo, and it gives rise to the lining of the digestive tract, respiratory tract, bladder, and urethra. It also forms the liver, pancreas, and thyroid gland.
• Option C: The nervous system is formed from the ectoderm. The ectoderm is the outermost layer of the embryo, and it gives rise to the skin, hair, nails, teeth, nervous system, and sense organs.
• Option D: Viscera and digestive system are formed from the endoderm. The endoderm is the innermost layer of the embryo, and it gives rise to the lining of the digestive tract, respiratory tract, bladder, and urethra. It also forms the liver, pancreas, and thyroid gland.