What do subshells explain and why do we use them if we already have main shells

Asap : ) read the passage about the life of clara barton and the table below it. clara barton was born on december 25, 1821, in oxford, massachusetts. as a child, clara was very shy. she first found her calling while caring for her brother after he fell from a rafter in their barn. despite the fact that most teachers were still men at the time, clara became a teacher at the age of 15, as well as one of the first women to work for the federal government at the us patent office. in 1881, clara opened the first chapter of the american red cross in the united states and served as its first president. the american red cross is a relief organization that offers assistance to victims of such disasters as the 1889 johnstown flood and the 1900 galveston flood. she served as president for 23 years before resigning amidst claims that money was being mishandled internally. the civil war was a bloody war fought between the years 1861–1865. during the war, clara sought to the soldiers in any way she could. she collected needed supplies and distributed them to the union army. these supplies included items such as food, bedding, and clothing. however, clara was not content to sit on the sidelines; she often risked her own life to care for soldiers wounded in battle. for these deeds, she was nicknamed the "angel of the battlefield.” when the war ended in 1865, clara worked for the war department in various ways. in the table, what information best fits under the heading "what i learned about her accomplishments”? a. clara barton was born in 1821 in oxford, massachusetts, and was very shy as a young child. b. clara barton worked as both a teacher and for the federal government in the us patent office. c. clara barton cared for wounded soldiers during the civil war and started the first american red cross chapter in the united states. d. clara barton was president of the american red cross during the 1889 johnstown flood and the 1900 galveston flood.