The Hajj - Pilgrimage For Millions of Muslims

Read the text about the Hajj. Some lines have a word that should not be there. Write this word in the space at the end of each line. If the word is correct, write OK.

1 About two and a half million of Muslims come of
2 to Mecca for their annual pilgrimage, the Hajj. OK
3 The holy pilgrims come by plane, car and public
4 transport. Some walk at long distances to the
5 holy city.  
6 Every healthy Muslim must attend to the Hajj
7 at least once in a lifetime. They believe it that
8 a journey to Mecca will relieve them of their
9 sins. The five-day event, however, is not even
10 free of tragic incidents. Some crowds of people
11 are often crushed to the death.
12 Pilgrims meet them at the Great Mosque,
13 where they move around the Kaaba, such a
14 black stone.Then they go after to a camp in the
15 valley of Mina and climb up a rocky hill, Mount
16 Arafat.It is the other place where the Prophet
17 Muhammad has delivered  his last speech.
18 When they retrace the same route that the
19 Prophet went over 14 centuries ago.
20 For many Muslims around the world the Hajj
21 is never a once in a lifetime experience. Some
22 save off money their whole life so that they
24 can travel to Mecca before.