1. A plant sits on a window sill. Over time the stems of the plant curve toward

1. A plant sits on a window sill. Over time the stems of the plant curve toward the light coming in the window. This process is calledA. phototropism.B. photoperiodism.C. gravitropism.D. phytochromism.2. Which of these parts receive nerve impulses from the central nervous system causing muscle fibers to contract?A. InterneuronsB. Motor neuronsC. Sensory neuronsD. Myelin sheaths3. In the human immune system the main function of the _______ is filtering blood.A. thymus glandB. spleenC. tonsilsD. appendix4. In flowering plants which of these becomes the female gametophyte?A. MicrosporeB. Pollen grainsC. Pollen sacsD. Megaspores