Hint:Breathing is a mechanical process. It includes taking air in the respiratory organs also known as inspiration, and exhaling the air out also known as expiration, by altering the volume of the bucco-pharyngeal cavity, acting like a force pump.
Complete answer: Respiration is a procedure in which food is oxidized with oxygen to give out energy. The energy given out is used to do many life activities. The metabolic waste like carbon dioxide is removed from the body. Because of the amphibious style of life, frogs show diverse ways of respiration. The exchange of gaseous occurs in following 4 ways: -Gill respiration -Cutaneous mode of respiration -Bucco-pharyngeal mode of respiration -Pulmonary mode of respiration
Breathing takes place in two steps: >Inspiration: It is the intake or inhalation of fresh air from the atmosphere in the lungs for exchange of gases. The channel of air from outside in the bucco-pharyngeal cavity is so-called aspiration. The procedure by which lungs are occupied with fresh air is so-called pulmonary inspiration.
>Expiration: Expiration is the process of elimination of air from the lungs to outside. It is also called pulmonary expiration. It is the giving out or exhalation of carbon dioxide from lungs, returning back to the bucco-pharyngeal cavity via glottis and to outside.
Air circulation of lungs is hampered by oscillatory or lowering and raising of the bucco-pharyngeal cavity. This movement of bucco-pharyngeal cavity is carried out by two sets of muscles which are sternohyoid muscles that are attached anteriorly to the inferior surfaces of hyoid bone and posteriorly to sternum bone, and the petrohyoid or petrohyal muscles connected anteriorly to squamosal bone and posteriorly to higher surfaces of hyoid bone.
Additional information: Sternohyoid or sternohyoid muscle is located underneath the mouth cavity. It joins hyoid and sternum. The mouth cavity is lowered downwards when it contracts. The petrohyal muscle lies outside the mouth cavity and the upper and lower ends connect squamosal bone and hyoid respectively. The mouth cavity is pushed upwards when it contracts.
Thus the correct answer is option ‘B’.
Note:Pulmonary respiration occurs between the buccal respirations. During the process, the buccal cavity acts as a force pump. The down and up movements of the surfaces of buccal cavity is done by the action of sternohyal and petrohyal muscles.