Answer:
C. 30
Step-by-step explanation:
circumference of the semicircular plot
[tex]=\frac{1}{2}\times\pi d+d\\\\=\frac{1}{2}\times 3.14\times 35+ 35\\\\= \frac{1}{2}\times 109.9+35\\\\= 54.95+35\\\\= 89.95\\\\No. \: of\: poles= \frac{89.95}{3}\\\\= 29.98\\\\\approx 30[/tex]