There are many flowers and trees on ________ sides of the Century Road.
A:each
B:every
C:both
D:all
放久的馒头会长出“白毛”或“黑毛”,这些霉菌来自于( )
(2015•无锡)小明利用18cm长的吸管、细铜丝、石蜡等材料自制密度计.