Last year Sonny . . . . . . . . four miles each morning before breakfast, but he . . . . . . . . around the block each morning instead since his heart attack.

n the first part of the sentence, "Last year Sonny ran four miles each morning before breakfast," the simple past tense (ran) is used to indicate an action completed in the past.

In the second part of the sentence, "but he has been walking around the block each morning instead since his heart attack," the present perfect continuous tense (has been walking) is used to describe an ongoing action that started in the past and has relevance in the present.

The correct combination is ran, has been walking in Option A.