如图所示，飞船从圆轨道l变轨至圆轨道2，轨道2的半径是轨道l半径的3倍。若飞船在

 Laboratory　work　is　your　chance　to　learn　science　firsthand.　It　can　be　fun　but　you　must　be　careful　to　prevent　injury.　Listen　closely　when　your　teacher　reads　and　explains　the　rules　before　your　first　lab　lesson.
LABORATORYRULES
Throughout　the　lesson
·Do　not　enter　the　science　lab　without　the　teacher’s　permission.·No　food　or　drinks　are　to　be　alowed　in　the　science　lab.
Before　the　Experiment
·Read　al　instructions　carefuly　before　every　experiment.
·Prepare　al　apparatus（仪器）and　arrange　them　so　that　you　wil　not　knock　them　over　while　doing　the　experiment.
During　the　Experiment
·If　you　are　unsure　of　how　to　use　any　apparatus　or　how　to　operate,　ask　your　teacher　for　help.·Never　smel　or　taste　chemicals　unless　your　teacher　gives　permission.
After　the　Experiment
·Wash　al　apparatus　after　use　and　return　them　to　the　places　where　they　were.
·Throw　waste　materials　in　proper　waste　baskets.　　　　First　Aid　　　　
·Report　al　accidents　to　your　teacher　immediately.
·If　you　spil（ 溅 出 ）any　chemicals　onto　your　body　or　clothing,　wash　with　plenty　of　water　and　report　to　your　teacher.
小题1:　Your　teacher　wil　probably　tel　you　the　rules　above　_____　the　first　lab　lesson.

A．before

B．since

C．during

D．after

小题2:　Before　every　experiment,　you　should　_____.

A．taste　the　chemicals　first

B．clean　al　the　apparatus

C．read　al　instructions　carefuly

D．report　al　the　accidents　to　the　teacher

小题3:　When　you　are　not　sure　how　to　use　al　apparatus,　_____.
A.　try　them　on　your　own
B.　read　the　rules　carefuly
C.　ask　your　teacher　for　help
d.　put　them　back
小题4:　It　is　clear　that　you　can　_____.

A．bring　food　into　the　lab
B．enter　the　lab　anytime
C．smel　chemicals　as　you　like	D．learn　science　directly　in　the　lab

小题5:　If　you　get　chemicals　on　the　clothing,　you　can　find　ways　to　solve　it　in　the　part　_____.

A．Before　the　Experiment

B．First　Aid

C．During　the　Experiment

D．After　the　Experiment