汽油的闪点是()℃。

单项选择题Fill in the blank with the most appropriate choice. The results of this study indicate that advanced composite structures used in payload fairings ___________ promising opportunities for cost reduction.

单项选择题turtle.circle(50, steps=3)的效果是( )。 A、绘制一个半径为50的圆 B、绘制一个直径为50的半圆 C、绘制一个半径为50的圆，分三次画完 D、绘制一个三角形