El sistema circulatorio y respiratorio trabajan de manera coordinada. Cuando tu cuerpo necesita más oxígeno, ¿cómo responde el sistema circulatorio? *

a. El corazón late a un ritmo más rápido para igualar el aumento en frecuencia respiratoria.
b. Envía menos sangre a los pulmones y al resto del cuerpo.
c. La sangre se mueve más lentamente para transportar más desechos.
d. Los vasos sanguíneos se contraen para conservar el oxígeno.

b

is correct hope this   also i learnd this in middle school

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.

protistas excret ethanol used in the manufacture of vinegar