PRESENT PERFECT SIMPLE or PRESENT PERFECT CONTINUOUS?

Decide if the sentences below are best completed by verbs in the present perfect simple tense or the present perfect continuous tens.  Choose the appropriate option for each gap from the drop down menu.

1. For the last ten years all Polish governments 
   have been trying

   have tried
    to clean up Polish rivers but a lot needs to be done before our rivers are completely free of pollution.
2. The local authorities in Warsaw 
   have built

   have been building
    a new wastewater treatment plant.  The 'Czajka' may have cost € 600 million but, at last, untreated sewage is no longer routinely discharged straight into the Vistula in the Polish capital.
3. Salmon 
   has not been seen

   has not been seeing
    in the Vistula since the Włocławek dam was built in 1970.
4. Scientists 
   have known

   have been knowing
    for decades that air pollution causes lung disease and even cancer.  So far, their arguments 
   have not convinced

   have not been convincing
    Polish politicians that this problem needs to be dealt with urgently.
5. Since (=because) Poland 
   has not met

   has not been meeting
    the deadline for enforcing the EU standards of air quality, the European Commission 
   has been threatening

   has threatened
    to take the Polish government to court over poor air quality in our country
6. The last coal mine in Great Britain 
   has been closed

   has been closing
   .  Britain plans to rely on the North Sea oil, gas and imports from abroad.
7. Environmental issues 
   have never seemed

   have never been seeming
    to matter more than at the present moment.  The COP 21 climate change summit in Paris is clear evidence of that.  
8. The environmentalists 
   have always believed

   have always been believing
    that protecting the environment is more important than economic growth.  This belief seems to be increasingly popular among members of the public in western Europe (though not in central or eastern Europe).
9. Ever since the collapse of communism Poland 
   has been trying

   has tried
    to catch up with the ‘old’ EU countries in terms of GDP per head of population.  So far, we 
   have managed

   have been managing
    to overtake Greece and Portugal and we are likely to catch up with Spain very soon.
10. Poland 
    has never been

    has never been being
     richer than Germany but the cost of feeding and housing millions of illegal immigrants may make our western neighbour bankrupt.  So who knows what will happen in the future?