For each of these sentences choose the corect alternative,present simple or present continuous.
1.About 1,000 people visit/are visiting Machu Picchu every day.
2.The mountains in Peru are/are being over 4,000 metres high.
3.I don't understand/am not understanding why people like camping.
4.We spend/are spending three days camping in the mountains next week.
5.The paths become/are becoming worn away by tourists.
6.Do people drop/Are people dropping litter in your street?
7.She studies/is studying microbiology at university at the moment.
8.I think/am thinking the sea is too dirty to swim in.
9.The River Amazon flows/is flowing into the Atlantic Ocean.
10.The number of tourists increases/is increasing fast.