$1$. It is very useful and when you go to a cave
$2$. Mount Everest is the highest mountain in the world
$3$. If we had a map, we would not get lost
$4$. A trip to the Himalayas is an unforgettable experience
$5$. It is necessary to do the homework
$6$. Is building taller than house ?
$7$. There are a lot of modern houses in the center of the city
$8$. It's 2km from my home for the downtown