Which lines best contributes to the suspense built in the passage? a. the secular cooling that must someday overtake our planet has already gone far indeed with our neighbour. b. it has air and water and all that is necessary for the support of animated existence. c. its physical condition is still largely a mystery, but we know now that even in its equatorial region the midday temperature barely approaches that of our coldest winter. d. the immediate pressure of necessity has brightened their intellects, enlarged their powers, and hardened their hearts.