The daily energy requirement for an individual varies significantly based on factors such as age, sex, body weight, and level of physical activity. A "hard worker" implies a person engaged in heavy physical labour. While individual needs differ, a common estimated range for men engaged in heavy activity is typically 3000-4000 kcal or more per day. Among the given options, 4000 Kilocalories is the most appropriate estimate for the daily energy required by a man doing hard work.