G.Bitcoin was introduced on the Internet in 2008 by a software developer called Satoshi Nakamoto.

3、根据短文内容，从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

　　It could happen anywhere at any time． 1 Most people，at one time or another，have been on the receiving end of a random act of kindness．In a sometimes cold world where people can be so focused on what they're doing，a random act of kindness can make all the difference．

　　They can be relatively insignificant．Hannah Bailey from London，for example，told the Metro newspaper about how she was given her fruit and vegetable shopping for free．The seller did her a kindness when it emerged she didn't have any change to pay． 2

　　The city of Naples has long had a tradition called'caffè sospeso'．When buying coffee，a person who has recently been lucky would purchase two cups but only drink one，leaving the second one anonymously(匿名)，out of the goodness of their heart，for a poor person to claim for free． 3

　　However，in some cases，these little acts can be a matter of life and death．Take，for example，the unnamed commuter，who in June 2018 fell off a station platform onto an electric railway track in Toronto，Canada．A quick-thinking，hut even now unknown，bystander selflessly leapt down to pull him to safety．

　　So，why do it? 4 The people never meet again．According to UK charity The Mental Health Foundation，acts like these can"give our lives new purpose，show us other perspectives on our own problems and even make us feel content．"

　　 5 Hold open a door for someone，deliver a compliment-even give up your seat on a bus．Help someone who is in need．It takes all kinds．It needn't be anything huge．One day，whether you need it or not，someone might help you in your hour of need．

A．So give it a try．

B．Be brave to face challenges．