发绀是指100ml血中还原Hb大于（） A.3g B.4g C.5g D.6g E.

     The best time to go to Beijing is fall. It's 1._________ and cool. You can go to the Great Wall. When
is the best time to go to Harbin? Of course2.__________. It's windy and cold. But you can 3._______
there. 4._________ is the best season to go to Sanya.  It's sunny and hot. You can 5. _______ in the sea. What about Hangzhou? 6.________ is the best time to go there.The sky is 7.________. The leaves are
8._____. It's beautiful. You can 9._____________, too.