Even if you could travel into the past, there is something called the "grandfather paradox". It asks what would happen if a time traveler were to go back in time and have his own grandfath-er killed for some reason, and therefore prevent himself from being born．If the time traveler was not born, how would he travel back in time？

　　And would you really like to visit the future In H.G. Wells' book,the main character travels into distant time where he arrives at a beach and is attacked by giant crabs.He then voyages 30 million years into the future where the only living thing is a black object with tentacles（触角）. If that's what's in store, maybe we are better just living in the present day after all．

23. The novel The Time Machine mentioned in Paragraph 2 aims to show___________．

A．People's interest in time travel

B．the special feature of the book

C．the long history of time travel

D．the contribution of H.G. Wells

24. Einstein's and Hawking's theories_________．

A．have similarities in many ways

B．push the invention of the first spaceship

C．have proved wrong by some time travelers

D．suggest the possibility to invent the time machine

25 .In Paragraph 4,"grandfather paradox"probably refers to the idea that__________．

A．the traveler is prevented from meeting his grandfather

B．the traveler goes back in time to seek for his grandfather

C．the grandfather's death makes the traveler's birth impossible

D．The reunion of the traveler and his grandfather brings happiness

第二节

One very important component of optimism is gratitude or feeling grateful. In fact, there is a strong connection between a grateful attitude and a heightened sense of well-being. Appreciate all the positives in your life by starting a gratitude journal in order to remember what you're grateful for.