Correct Answer - Option 4 : 5%

**Explanation**

__As per IS 456:2000, clause 39.4,__

__Compression Member with Helical Reinforcement__

The strength of compression members with helical reinforcement shall be taken as 1.05 times the strength of similar member with lateral ties provided the condition

\({Volume\; of\; helical\; reinforcement\over Volume\; of\; the\; core}\lt0.36\left( {\frac{{{A_g}}}{{{A_c}}} - 1} \right)\frac{{{f_{ck}}}}{{{f_y}}}\;\)should be satisfied.

where

Ag = gross area of the section

Ac = area of the core of the helically reinforced column measured to the outside diameter of the helix

fck = characteristic compressive strength of the concrete

fy = characteristic strength of the helical reinforcement but not exceeding 415 N/mm2

Hence, the load-carrying capacity of the column with helical reinforcement is increased by 5% due to increased strength as a result of better confinement.