1. Clara b. es de Paraguay. - Since she was born there, you use es.
2. A. Estas tu en Asuncion? - Since you are currently there, you use estas - this might change.
3. Nosotros C. somos altos. - Since this is a permanent state, you use somos.
4. Ellos A. estan cansados. - Since this may change, you use estan.