少不了: cannot do without, to be unavoidable, are bound to be many...
题材: subject matter...
坡: slope, sloping, slanted...
密封: to seal up...
话题: subject (of a talk or conversation), topic...
高速公路: expressway, highway, freeway...
设立: to set up, to establish...
松弛: to relax, relaxed, limp, lax...
慢性: slow and patient, chronic (disease), slow to take effect (e.g. a slow poison)...
临时: as the time draws near, at the last moment, temporary, interim, ad hoc...
