What does infinitesimal mean? Can you use it in a sentence?

Which statement best summarizes this excerpt from leo tolstoy's the death of ivan ilyich? and in imagination he began to recall the best moments of his pleasant life. but strange to say none of those best moments of his pleasant life now seemed at all what they had then seemed—none of them except the first recollections of childhood. there, in childhood, there had been something really pleasant with which it would be possible to live if it could return. but the child who had experienced that happiness existed no longer, it was like a reminiscence of somebody else.

One way to show a character is a) to use dialogue b) use dynamic sentences c) interview friends d) share details

Would the essay be more or less effective in explaining the concept of dead reckoning if you knew from the beginning that ahmed is an ant?