Hint: These are the diseases which are mainly differentiated on the basis of their transmission as one of the diseases can spread to others but the other one doesn't get spread to others.
First of all, you should know what these diseases are to solve this question easily. Communicable diseases are those diseases which are caused by pathogens such as viruses, bacteria and these can spread from one person to another, for example, HIV, hepatitis A, hepatitis B. These can be spread by direct or indirect sources like wind, water etc. This can be treated by conventional methods.
Non-communicable diseases are those diseases which don't get spread from one person to another or you can say it is non-transmissible. These are caused due to allergies, abnormalities in cell proliferation, malnutrition etc. Examples are cancer, allergies, heart disease etc. This can be treated by surgical methods.
Now let's look at all the options.
> Option A says NCD can be treated by CD cannot. This is not true, both the diseases can be treated but methods of treatment are different for both.
> Option B is that CD can spread to others whereas NCD cannot. This is true as per the above explanation.
> Option C is that CD can be treated but NCD cannot. Again the same thing, both of the diseases can be treated but the methods are different for the treatment.
> Option D is NCD can spread to others whereas CD cannot. But in actual Communicable disease can spread from one person to another whereas Non-communicable doesn't get spread from one person to another. Now it is clear that CD can spread to others whereas NCD cannot.
Hence, The correct answer is option (B).
Note: As the name indicates, communicable diseases are the one which can be transmitted from one person to another for example AIDS whereas non-communicable means the one which cannot be transmitted from one person to another. From these main points you can easily answer the question related to these diseases.