23. Why are US public health experts not very concerned by the new variant?
(A)Flights to and from the UK have been cancelled.
(B)People in the USA are developing immunity from coronavirus.
(C)This was anticipated by health experts and vaccine developers.
(D)The US healthcare system is coping extremely well with coronavirus cases.
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統計: 尚無統計資料
統計: 尚無統計資料