Underground exploring (UE) involves traveling through tunnels and other hidden parts of acity. Starting in the 1970s, a movement called urban exploration took special notice of    36    visited parts of the underground environment like tunnels, drains and abandoned subway stations.Perhaps because people are fascinated by hidden things, underground spaces have always had aunique    37    to explorers. But in fact, underground exploring can be illegal, and the police oftenarrest UE groups as they emerge from tunnels and charge them   38    trespassing. Unbanexplorers generally take a very liberal approach to property rights. They tend to   39   that aslong as they are not damaging anything, they have the right to use the property. MIT was only oneof several hot spots for UEs. Students at the Massachusetts Institute of Technology developed atradition of exploring the steam tunnels at the university   40   the fact that it was illegal.Informal groups similar to the MIT group explored the undergrounds of Paris, Toronto and Sydney.
【題組】36.
(A) rare
(B)rarely
(C)frequent
(D) frequently