your answers are correct
answer: 1. we used to live in the country. now we live in the city.
2. we are getting used to living in the country. it's a much slower pace.
3. we are used to living in the country. we have got many friends here.
option d is a contraction of the words it is so, option d is the right answer.
the first thing you would do is try and understand the prefix. let's say the prefix was "anti-" then you would know that the prefix means against the base word. i hope this !