It is the last choice because their similar bone structures suggest they once had a common ancestor, which is why they are all mammals.
Answer:
Relief, elevation, and landforms
Explanation:
Topography is the shape of a land. It's elevation, land form, and relief.
Environment, predators, and natural selection.
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Answer:
The oxygen cycle is closely linked to the carbon cycle and the water cycle (see hydrological cycle). ... Carbon dioxide enters the carbon cycle or is taken up by plants for photosynthesis. During photosynthesis oxygen is evolved by the chemical splitting of water and returned to the atmosphere
Explanation:
Answer:
The correct answer would be d. thymus.
The thymus is a specialized lymphoid organ of an immune system.
It serves as the site for training and maturation of T-lymphocytes or T cells.
It is composed two identical lobes each containing outer region termed as cortex and inner region termed as medulla.
T-cells are first trained and selected in the cortex region via positive selection. In this, T cells which are able to bind to foreign antigens are selected and rest are degraded.
The selected T cells then move in the medulla region where they are selected by negative selection. In this, the T cells which binds to self-antigens are degraded and rest survive to become functional T cells.
