In a chemical reaction, if a color change is detected, if an odor change is detected, or if a precipitate is formed, then:

a chemical reaction has definitely occurred

only physical reactions have occurred

a chemical reaction may have occurred

both physical and chemical reactions have definitely occurred

idk

explanation:

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.