The difference in time between Kolkata and London is:

Kolkata (following Indian Standard Time, IST) is located at $82^{\circ }30^{\prime }\text{E}$ longitude, which places it $5$ hours and $30$ minutes ahead of Coordinated Universal Time / Greenwich Mean Time (UTC/GMT $+5:30$). Since London observes GMT during winter, Kolkata is exactly $5.5$ hours ahead of London (and $4.5$ hours ahead during British Summer Time). Thus, "Kolkata is more than 5 hours ahead" is the correct option.