Final answer:
US involvement in Afghanistan began in 2001 and continued well into the 2010s, with the US military focusing on counter-insurgency, support for the Afghan government, and rebuilding efforts. The correct answer to the student's question is D: continued into the 2010s.
Step-by-step explanation:
The involvement of the United States in Afghanistan began in 2001. This action, known as Operation Enduring Freedom, was initiated in response to the September 11, 2001, attacks and aimed at overthrowing the Taliban regime and disrupting the operations of the al-Qaeda network. The U.S. military focused on rebuilding civil society and infrastructure in Afghanistan along with supporting a democratically elected government. Despite intentions to withdraw troops within a certain timeframe, challenges such as the Taliban insurgency and the drug trade persisted, thereby extending the US presence in the region.
By 2010, troop levels had increased to around 100,000 as the U.S. government continued its efforts against the insurgency. It was not until May 2014 that President Obama announced the end of most U.S. combat operations in Afghanistan, although a residual force remained to continue training Afghan security forces. A complete withdrawal was planned by the end of 2016, with the exception of a small number to defend U.S. diplomatic posts.
In summary, the US engagement in Afghanistan lasted well into the 2010s, with significant military involvement and efforts to stabilize the country. Therefore, the correct answer to the student's question is that U.S. involvement in Afghanistan continued into the 2010s, making option D the correct choice.