When preparing a tlc slide of a reference standard material (rsm), a solvent or mixture of solvents is used to dissolve the rsm and transfer it into the tlc plate. how does its polarity affects the rf of the rsm?

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

because natural gas is colorless, odorless, and tasteless, distributors add mercaptan (a chemical that smells like sulfur) to give natural gas a distinct unpleasant odor (it smells like rotten eggs). they locate the types of rock that are likely to contain natural gas deposits.