With no explanation, label text_A→text_B with either "DON'T KNOW", "NO" or "YES".
text_A: The historical calving grounds were unknown but might have been along southern Chinese coasts from Zhejiang and Fujian Province to Guangdong, especially south of Hailing Island and to near Hong Kong. Possibilities include Daya Bay, Wailou Harbour on Leizhou Peninsula, and possibly as far south as Hainan Province and Guangxi, particularly around Hainan Island. These areas are at the southwestern end of the known range. While the full extent of the whales' normal range in earlier times are unknown, there is evidence of the mammals regularly inhabiting the Gulf of Tonkin. In addition, the existence of historical calving ground on Taiwan and Penghu Islands (with some fossil records and captures), and any presence in other areas outside of the known ranges off Babuyan Islands in Philippines and coastal Vietnamese waters beyond the Gulf of Tonkin are unknown. There is only one confirmed record of accidentally killing of the species in Vietnam, at Ngoc Vung Island off Ha Long Bay in 1994 and the skeleton is on exhibition at the Quang Ninh Provincial Historical Museum. Gray whales are known to occur in Taiwan Strait even in recent years.
text_B: Since most American readers will likely recognize the name of the Gulf of Tonkin for the role it played in the Vietnam War, would you say that the outbreak of the war, and the possibility of naval combat, gave whale biologists a legitimate reason to fear that useful fossil evidence could be destroyed (rather than just speculation based on the possibility of fossils existing there)?
YES.