China says World Health Organization (WHO) experts had access to all data or interviewees they requested when they conducted a joint COVID-19 study earlier in 2021. The WHO has asked for a follow-up mission, which China has rejected, and some of the mission's members are now saying that they did not have access to all the data they wanted. It's been nearly two years since the coronavirus first emerged. Rong Ying, vice president of the China Institute of International Studies, talks about why discovering the origins of this disease has become so controversial.