A body of mass 1 kg is attracted by the earth with a force which is equal to

We know that every body that has mass exerts a gravitational force on other body that also has some mass. Similarly, the earth also exerts a gravitational force on all the bodies on the earth. This is also called as the weight of the object.
According to Newton's second law, this force can be given as:
$\mathrm{F}=\mathrm{mg}$
Where m is the mass of the body, g is the acceleration due to gravity on the earth and the value of g is:
$\mathrm{g}= 9.8 \mathrm{m}/{\mathrm{s}}^2$

We have a body of mass 1kg. Substituting its value in the equation of force, we get, 
$\mathrm{F}=\mathrm{mg}=1\times 9.8$ 
$\mathrm{F}=9.8 \mathrm{N}$
Hence option A is the correct answer.