Question: Read the article and select the best answer. Article: BAGRAM, Afghanistan: A transport helicopter packed with US soldiers crashed near a military base just north of the capital, killing at least five of them and wounding seven others, the US military said yesterday. The cause of Sunday's crash, about 11 kilometers east of Bagram Air Base, was not immediately known. The US military said it was investigating, and it refused to take journalists from the base to the crash site. But after a long search, reporters found the wreckage in a remote area yesterday afternoon. It was broken into three pieces, some of which had fallen into a mostly dry riverbed. About 15 US soldiers were guarding the site. A statement sent by email from Central Command, in Tampa, Florida,on Sunday said,"Early reports indicate seven service members were killed," when the US military helicopter went down. At Bagram Air Base yesterday morning, US military spokesman Major Richard Sater said the plane was an MH-53 transport helicopter and confirmed that it was involved in all ongoing military operation, dubbed Mountain Resolve, taking place in the east of the country. He referred all other questions, including the numbers of casualties and the cause of the crash, to Central Command officials. Bagram Air Base, just north of the capital, is home to most of the peacekeepers patrol Kabul. In another development, three US soldiers were killed on Sunday in Iraq. Gunmen in Mosul shot two American soldiers driving through the city center, sending their vehicle crashing into a wall. About a dozen swarming teenagers dragged the men out of the wreckage and beat them with concrete blocks, witnesses said. In recent weeks, attacks against US troops and their Iraqi allies--such as policemen and politicians working for tile interim Iraqi administration--have increased in the region surrounding Mosul. In Baqouba, just north of Baghdad, insurgents detonated a roadside bomb as a 4th Infantry Divison convoy passed, killing one soldier and wounding two others, the military said on Sunday. Question: The US helicopter crashed _ . Options: A: when it was investigating military operation B: when it was carrying out a task in Afghanistan C: when it was flying to Tampa, Florida packed with US soldiers D: when it was working for Afghanistan's military
Answer:
B