To find the angle of the sector representing labour in a pie chart, follow these steps:

1. Calculate the total cost of production:

\[
\text{Total Cost} = \text{Labour} + \text{Power} + \text{Materials} + \text{Miscellaneous}
\]

\[
\text{Total Cost} = 70 + 15 + 30 + 5 = 120
\]

2. Determine the fraction of the total cost that is due to labour:

\[
\text{Fraction for Labour} = \frac{\text{Labour}}{\text{Total Cost}} = \frac{70}{120}
\]

Simplify the fraction:

\[
\frac{70}{120} = \frac{7}{12}
\]

3. Convert this fraction into an angle for the pie chart:

The total angle in a pie chart is \(360^\circ\).

\[
\text{Angle for Labour} = \frac{7}{12} \times 360^\circ
\]

\[
\text{Angle for Labour} = 7 \times 30^\circ = 210^\circ
\]

Thus, the angle of the sector representing labour in the pie chart is:

A. 210°