___________ he is tired, he is still doing his homework.
A:Because
B:As
C:When
D:Although
x÷1.6=7, 方程两边同时____就能求出x的值。
He is really annoying because he always makes fun of others.
其中D处放有干燥的紫色石蕊试纸,E处放有湿润的紫色石蕊试纸,F、G处依次放有喷上少量淀粉KI溶液、浓NaOH溶液的棉球.回答下列问题: