Вопрос по английскому языку:

Circle the correct.
1. My dog ..... understand about 20 words in Spanish.
a) can to b)can c)is able
2.But he ..... understand one word of English.
a)doesn`t can b)can`t c)can not
3.When the people ... the survivor, their dogs helped them.
a) couldn`t find b)can`t found c)couldn`t found
4.My dog ... very fast.
a)doesn`t can run b)can`t run c) cannot runs