The question is asking which connective tissue keeps body heat in. Go through the four tissue types on the list and check what each one is actually built to do.
- Areolar tissue: This is the loose "packing" tissue that fills gaps between organs and under the skin. It holds things in place and allows some flexibility, but it has no special fat store for insulation.
- Adipose tissue: Its cells (adipocytes) are almost entirely filled with stored fat. Fat conducts heat far more slowly than muscle or blood, so a layer of adipose tissue under the skin traps body heat and slows its escape to the surroundings.
- Reticular tissue: This forms the fine mesh-like framework inside organs such as the spleen and lymph nodes, supporting cells there. It has no thermal role at all.
- Tendons: These are dense bands of collagen that anchor muscle to bone so force can be transmitted. They are built for tension, not for storing heat.
Out of the four, only adipose tissue is structured (fat-filled cells packed under the skin) in a way that slows heat loss, which is exactly what thermal insulation means.
Let's summarize:
- Insulation depends on a poor heat conductor sitting between the body core and the cold outside, and fat plays that role.
- Areolar tissue, reticular tissue and tendons are all built for support or anchorage, not for heat retention.
So adipose tissue is the tissue providing thermal insulation.