There has been an increase in the number of peopl

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There has been an increase in the number of people infected with HIV in Eastern Europe and Central Asia mainly because__________.

A.most people were infected when staying in developed countries in the past

B.there were more cases of HIV present

C.in some countries more infected needles were used for the injection of drugs

D.HIV reports were written with more points in these countries

热搜:n维列向量组a1,an-1线性无关,且与非零向量正交