Kelly works in a restaurant as a waitress in her spare time, so we can say she does a ________ job.
A:busy
B:full-time
C:part-time
明代诗人曾写下这样一首诗:“空手把锄头,步行骑水牛;人在桥上走,桥流水不流”.其中“桥流水不流”之句应理解成其选择的参照物是( )
某同学用两个硬纸筒探究小孔成像,如图所示。