Conjunctivitis may be caused by bacteria, viruses, allergens, or irritants. What signs and symptoms differentiate bacterial conjunctivitis from other types ？（）
A．Subacute onset, severe pain, and preauricular adenopathy.
B．Recurrent onset, no pain, and clear discharge.
C．Acute onset, moderate pain, and purulent discharge.
D．Acute onset, mild pain, and clear discharge.
参考答案：C
解析：
Bacterial conjunctivitis has an acute onset, moderate pain, preauricular adenopathy, and a copious and purulent discharge. Viral conjunctivitis has an acute or subacute onset, mild to moderate pain, preauricular adenopathy, and moderate and seropurulent discharge. Allergic conjunctivitis has a recurrent onset, no pain, no preauricular adenopathy, and moderate and clear discharge. Irritant conjunctivitis has an acute onset, mild pain or no pain, rare preauricular adenopathy, and minimal and clear discharge.