11. which of the following events occurs first? a. the brain sends a signal to the muscles. b. the blood vessels just under your skin become narrow. c. the hypothalamus detects a drop in body temperature. d. you shiver.

The correct answer is option C.

The organ system of the body functions in combination to maintain homeostasis unconsciously and consciously. They spontaneously amend towards the changes in its outer surrounding to maintain the internal environment at optimal levels for the health.

Hypothalamus is the part of the brain, which helps in maintaining the internal balance of the body. It is the part of the brain, which monitors the activities, like body temperature, hunger, and the discharging of various hormones.

In order to maintain homeostasis, the drop in temperature of the body is first detected by the hypothalamus. After that, the signal is sent to the muscles, and then the blood vessels underneath the skin get constricted and one shiver.

estuaries are the partially enclosed coastal bodies of brackish water formed at the mouth of sea where river meets an ocean. it is a transition zone between river and sea water so estuaries are influenced to both marine environment such as tides, waves and to riverine such as flow of fresh water and sediments. the mixing of sea and fresh water provide high level of nutrients, making estuaries a high product habitats.

many estuaries suffers degradation from a variety of human activities like erosion from deforestation, overgrazing, overfishing, drainage and eutrophication.

so from the above statement answers will be

1. false as estuaries are formed due to both brackish and freshwater.

2.true, due to high productivity estuaries are breeding ground for many marine species.

3. direct and indirect activities of man that contribute to pollution and deposition of sediments.