The correct answer is B) Economizer section. The economizer section of the boiler is generally blown first and last when blowing tubes on an integral superheat boiler fitted with an economizer. This is because the economizer, being the last heat exchanger in the boiler system, is most susceptible to fouling and requires more frequent cleaning to maintain efficient heat transfer. Blowing the economizer section first and last helps to dislodge any accumulated deposits and ensure optimal boiler performance. The other options are incorrect because the superheater section, generating tube bank section, and screening tube section are not the primary focus of the tube blowing sequence, which is typically centered on the economizer.