Organize the items listed into the proper sequence of events for gas exchange.

a: O2 is transported to cells by circulatory system.
b: O2 is drawn into the lungs during inhalation.
c: Cells use O2 and generate CO2.
d: CO2 is exhaled.
e: The circulatory system transports CO2 to the lun

b, a,c,d  

Explanation:

option E is incorrect, that's why I didn't add it

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c is having 4 valence electrons and is bonded to three hydrogens and one sulphur atom, therefore, the number of bond pair is equal to four. as all the valence electrons are used in forming the bonds so, there is no lone pair left on carbon.

s is having 6 valence electrons and is bonded to one other sulfur atom and one carbon atom, therefore, the number of bond pair is equal to 2. as only two valence electrons are used in forming the bonds so, four electrons are left. therefore, two lone pairs are present on s.