Tennis player Maria Sharapova speaks 1 People in Istanbul speak
2 A lot of people in China speak
3 'Language' is a word in
4 Rafael Nadal speaks
5 'Guten Tag' is 'Hello' in
6 Au revoir' is 'Goodbye' in
The other language is

Do you know where the Mississippi River is?
THE is the definite article.   when you have ONE of something that is definite, you use THE.  there is only one mississippi river, so you must use 'the'.

'an' is an indefinite article, not appropriate. if you have one of something thats not specific such as 'an apple'. 

He will be twenty in a month.
'in a month' says this is in the future, so you need a future tense verb
'am' goes with 'I' always  (I am ...)
'is' is present tense, but you could say 'he is going to be twenty in a month'

We might go to Peru next year.  We're not sure.
'not sure' means it may not happen. 'might' is also uncertain
so 'should' means we need to do something

that's the woman whose son is an actor.
i am not sure why, just that this one is correct

This afternoon, we are going sandboarding
a) and b) are the same answer
'this afternoon' means future tense
'going to' states a plan or intention, where 'will' is used in a different sense, as in a promise or request for help

i'm bored of camping trips.  let's go on a safari
'for' is definitely wrong
i have heard 'from' used, but i suspect it is not proper grammar

извините за все английский, мой руский не достаточно хорошо.

Sample letter to a friend in english № 1dear michael,     thank you for your recent letter. it is so wonderful to hear from you!   i am very glad that you had a good vacation.     as for me, i also spent a wonderful vacation. first, i lived with my parents in the garden. the weather was hot and i  swam  a lot with my friends. we played soccer and rode bicycles.      and in august we went  to  cyprus   with my parents. it is a large island in the mediterranean with a wonderful climate. we swam in the sea and were lying in  the shade of huge eucalyptus trees. we traveled along the mountain paths and  played  tennis. anyway, it was a memorable summer.     how did your academic year begin?   are  there newcomers in your class? any new subjects?     i’m sorry, i have to go to the sports section.     all the best!     ivan sample letter to a friend in english № 2dear paul, thank you for your letter. i'm so glad to hear from you. it's great that you're on vacation in italy. you ask me how i spent the summer. i rested at a youth camp on the lake chebarkul is located in chelyabinsk region in russia. i can not say that the summer was very hot, but at the camp we had fun. we play games, play sports, go to the disco. as for me, i really liked the large and beautiful lake. moreover, i had a lot of new friends! and you have many friends? who's best friend? why are you friends with him? sorry, i must go. i look forward to hearing from you. best wishes, tanya sample letter to a friend in english № 3 dear paul, thank you for your letter. i'm happy to get it.in your letter you ask me how i spent my summer. i think that most people spend the summer on the shores of ponds, swimming and sunbathing. as for me, i spent the summer with his grandmother in the village. we walked a lot in the woods, picking berries and mushrooms. i've seen a lot of wild animals and birds. moreover, we met a large moose with huge antlers. i did not think that the forest is so interesting! how did you start out? there are new lessons? you learn in school last year? sorry, i have to go now.  write back soon!   best wishes, alex