so / because

She is tired (a)   she has walked for seven miles.

She has a lot of money (a)   she can buy that expensive coat.

The weather is hot (a)   the children are swimming now.

We didn't go to their party (a)   they didn't invite us.

We are too busy (a)   we can't go the cinema today.

It was cold (a)   I shut the window.

She doesn't like Andy (a)   he isn't honest and kind.

It was raining (a)   I took a taxi.

The water wasn't clean (a)   we didn't swim.

We walked home (a)   there were no more buses.