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【单选题】关于视网膜的感光细胞的叙述，错误的是
A.
存在视杆和视锥两种感光细胞
B.
中央凹处视锥细胞分布密集
C.
视杆细胞分辩能力差
D.
视锥细胞光敏感度差
E.
两种感光细胞的感光色素均有视紫红质
【单选题】A. No one should blind himself to the well-known fact.B. Heavy enquiries witness the quality of our products.C. We confirm cables exchanged as per copies(cable confirmation)herewith attached.D. I’m ne...
A.
listening is a perfect way to respond to others
B.
people keep silent because they don’t know the answer
C.
keeping silent means being too shy to speak
D.
it is easy to form the habit of listening silently