Nuclear energy has been a subject to controversy for many years. For some, nuclear energy should not be underutilized as it is considered the most environmentally friendly energy source. (1)____ coal and natural gas power plants discharge much carbon dioxide into the air, which causes a number of environmental issues, nuclear power plants’ carbon emissions are insignificant. (2) ____, disposal of radioactive waste during the production of the electricity can devastate mother earth. In addition, those who are for nuclear energy claim that it produces very inexpensive electricity. The cost of the uranium, which is utilized as a fuel in this process, is low. (3) ____ the fact, uranium is finite and exists only in few countries. It is pretty expensive to mine, refine and transport uranium. The other primary point of interest of utilizing nuclear energy is that (4) ____ the expense of setting up nuclear power plants is moderately high, the expense of running them is quite low. (5) ____, putting a plant requires permission form the authorities and is usually opposed by local people, which make some people less desirable to invest in it. Utilizing nuclear energy indeed has pros and cons, (6) ____ there are still many countries putting a lot of money and time into it. The most appropriate connective words to complete number 4 is ….

     Nuclear energy has been a subject to controversy for many years. For some, nuclear energy should not be underutilized as it is considered the most environmentally friendly energy source. (1)____ coal and natural gas power plants discharge much carbon dioxide into the air, which causes a number of environmental issues, nuclear power plants’ carbon emissions are insignificant. (2) ____, disposal of radioactive waste during the production of the electricity can devastate mother earth. 
      In addition, those who are for nuclear energy claim that it produces very inexpensive electricity. The cost of the uranium, which is utilized as a fuel in this process, is low. (3) ____ the fact, uranium is finite and exists only in few countries. It is pretty expensive to mine, refine and transport uranium. 
     The other primary point of interest of utilizing nuclear energy is that (4) ____ the expense of setting up nuclear power plants is moderately high, the expense of running them is quite low. (5) ____, putting a plant requires permission form the authorities and is usually opposed by local people, which make some people less desirable to invest in it. Utilizing nuclear energy indeed has pros and cons, (6) ____ there are still many countries putting a lot of money and time into it. 

The most appropriate connective words to complete number 4 is ….