Table 73 -Refer to Table 7

Multiple Choice

Table 7.3
$$\begin{array} { c c } \begin{array} { c } \text { Number } \\\text { of Workers }\end{array} & \begin{array} { c } \text { Total } \\\text { Output }\end{array} \\\hline 0 & 0 \\1 & 10 \\2 & 40 \\3 & 100 \\4 & 140 \\5 & 160 \\6 & 170 \\7 & 150\end{array}$$
-Refer to Table 7.3,which shows the number of workers and total output produced in a firm.Diminishing marginal returns set in with the addition of the _____

A) first worker.
B) third worker.
C) fourth worker.
D) fifth worker.
E) seventh worker.