未知题型 常见弓网故障主要由受电弓和接触网关系不良引起，包括：1、 ；2、 ；3、 。

未知题型 Choose a summary word from the list to complete the sentence. process; situation; finding; estimation; problem; difficulty; disruption; view Normal average human skin temperature is 37°C. At any lower environmental temperature, heat will be lost from the skin to the environment as the body attempts to heat up the air in direct contact with the body. This is known as conduction.

未知题型 （）是对个人决策、参与公共和文化事务以及经济生产所需要的科学概念和过程的知识和理解。