A calcium atom has 20 electrons . Electrons in the sub shell experience the lowest effective nuclear charge A . 1s
B. 2p
C. 3D
D. 4s

i believe you are right for all except the 3rd ( look at sqdancefan his answer is much better)

the dependant variable is spilled water

the independent is the heat

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.