John muir a) wrote a sand county almanac. b) opposed the national park system .c) established the sierra club.

C) established the sierra club

Explanation:

In 1860, he took his inventions to the state fair in Madison, where he won two awards. That year is when he enrolled at the University of Wisconsin. He studied Chemistry, Geology and Botany.

He began conducting research trips throughout the country, many of them on foot. He walked 1000 miles from Indianapolis to the Gulf of Mexico, then to Panama, crossed the isthmus and sailed by boat along the west coast, arriving in San Francisco in March 1868.

Author of more than 300 articles and 10 books where he narrated his travels and exposed his natural philosophy. In his articles for Century magazine, he drew attention to the deterioration of meadows and forests in the mountains caused by sheep and cattle. Congress declared Yosemite National Park in 1890.

In 1892, together with some of his followers, he founded Sierra Club, the first conservation group in history.