We know, the total surface area of cone=πrs+πr2,
where r is the radius of the base of the cone and s is the slant height.
Given, the total surface area of cone=920 m2 and r=14 m.
Let, π=3.14.
Substituting the values in the formula we get,
⇒940=3.14×14s+3.14×142
⇒940=43.96×s+3.14×196
⇒940=43.96×s+615.44
⇒940−615.44=43.96×s
⇒324.56=43.96×s
⇒s=324.5643.96
⇒s=7.38≈7 m.
Therefore, option A is correct.