)树枝属于散置障碍物(“散置lba3碍物”是自然物体,它包括:石bR4N、树叶、树枝、树杈等物体5xEX
BillandMelindaGatessharetheir2018AnnualLetter,“The10ToughestQuestionsWeGet.”Inthisyear’sletter,the10thonethatthey’vewritten.