Robert decides to go for a run when he gets home from school. as he begins running, his breathing rate starts to increase. what are the mechanisms that cause his breathing rate to increase? a. when carbon dioxide levels in the blood decrease, the respiratory center sends signals to the alveoli to increase the volume that they expand. b. when oxygen levels in the blood decrease, the respiratory center sends signals to the diaphragm to increase the rate at which it contracts and relaxes. c. the respiratory control center senses the need for more oxygen, which causes the trachea to push and pull air more forcefully. d. the diaphragm senses the need for more oxygen, which causes it to expand and contract more quickly in order to inflate and deflate the lungs.

The correct answer is option B which is low level of oxygen in blood is sensed by the brain respiratory center which signals the diaphragm to increase the rate at which it contracts and relaxes.

one is through turgidity. this occurs before ground tissue ( collenchyma

and sclerenchyma cells) become well

developed to give structural support to the plant as it grows bigger. the xylem

tissue (composed of rigid tissue) of the young

plant render this support and also maintaining osmotic turgidity of the surrounding

plant cells.

the water is warmed up by the sun and then it evaporates into the atmosphere. the sunlight warms the water by its heat. water is then cooled down and condensation takes place. the water then finally returns back to the earth by the process of precipitation in the form of rain or ice.

explanation: