A:required
B:intended
C:admitted
D:supposed
Bai Ling was happy yesterday. Because it was her father's birthday. She boughtgifts for him. And they took pictures in the park. In the afternoon, they ate delicious food. Bai Ling has a pen pal. He is Pat. He lives in the US. Yesterday he came here. He sang and danced. Oh, he also bought gifts. We had a good time.
如图所示是一种液面升降监测装置原理图.电光源S发出的一束激光与水平液面成50°角射向平静的液面,入射光线与反射光线的夹角为 ____ ;光经液面反射后射到页面上方水平标尺上的S′点,当液面下降时,光点S′将 ____(选填“向左”、“向右”或“不会”).