The correct answer is: C. Nineteenth
According to a report by Opensignal, Patna city ranked 19th among 20 cities in India as per availability of 4G signals between December 2017 to February 2018. The report found that Patna had an average 4G availability of 75.6%, which was lower than the national average of 80.3%.
The report also found that Patna had an average 4G download speed of 12.3 Mbps, which was lower than the national average of 13.8 Mbps. The report also found that Patna had an average 4G upload speed of 5.2 Mbps, which was lower than the national average of 6.2 Mbps.
The report concluded that Patna had a good 4G network, but there was room for improvement. The report recommended that the government and telecom operators work together to improve the 4G network in Patna.
The other options are incorrect because they do not represent the correct rank of Patna city among 20 cities as per availability of 4G signals between December 2017 to February 2018.