Out of following which ganglia unite to from nervering in nervous system of Cockroach ?

• A. Suboesophageal, supraesophegeal and circum oesophageal commisures unite to form nervering.
• B. Three ganglia in thorax region and six ganglia of abdominal region unite to form nervering.
• C. Three pairs of ganglia in thorax region and six pairs in abdominal regions.
• D. Three pairs supraoesophageal and one pair suboesophageal ganglia unit to form nervering.