A

Step 1: Calculate the gravitational force acting on the man.
The weight (force) is given by:
\( F = m \cdot g = 70\, \text{kg} \cdot 10 \text{m/s}^2 = 700\, \text{N} \)
Step 2: Calculate the work done against gravity while climbing a height.
The work done against gravity for a height 'h' is:
\( W = F \cdot h = 700\, \text{N} \cdot h \)
Step 3: Since the man climbs at a speed of 1 m/s, the time 't' taken to climb a height 'h' is:
\( t = \frac{h}{1 \text{m/s}} = h \)
Step 4: Power developed is given by the formula:
\( P = \frac{W}{t} = \frac{700 \cdot h}{h} = 700\, \text{W} \)
Therefore, the power developed by the man is 700 W.