当安全阀进口和容器之间串联安装爆破片时，应满足下列哪些条件( )。A．容器内的介质

     The mountain town of Canton is at an elevation(海拔) of
6,000 feet. It is   1   by thick underbrush and pine trees.
Because of six years of drought, thes   2   are a major fire
danger. Thousands of trees and tons of underbrush are going to
be   3   over the next five years at a minimum cost of $ 3
million. The   4   will be removed first,  then the trees will
be overturned and removed. A cleared nonflammable area will
then  5 surround the town of 4,000.
     Residents look forward to the work,   6   it will help
their town survive a future inferno(地狱). "But there are two
  7    ," said one resident. "All the extra trucks are going to
make traffic    8    bad. Once the area is cleared, we have to
make sure dirt bikers don't try to make the     9     area their
personal playground. "
    A recent fire burned 4,000 acres and destroyed 11 homes
in 10 Hamilton. The fire was raging(汹涌)toward Canton,
but a sudden rainstorm  11  the fire. Residents know that
they won't get lucky twice, so they are    12      this massive
clearing operation.
    Ninety percent of the cutting and clearing will be paid
  13   federal funds. Unfortunately, if the trees are on private
property, they must be paid for by the residents  14  . Prices
can range as high as $1,000 to cut and remove one tree.
  15     say that residents can apply for state and federal loans
if   16  .
     "Well, what good does that do me?" asked Thelma, a 65-
year-old widow. "I'm living on  17  security. I've got four
trees on my property. The government's not going to  18 
me money when they know there's no way I can pay it back.
  19  what am I supposed to do? These planners with all their
big ideas ought to think of the 20  people. "