21. In accordance with 46 CFR Subchapter I (Cargo and Miscellaneous Vessels), which of the listed fire extinguishers would be considered hand portable/semi-portable and capable of combating a class «B» fire?

46 CFR Subchapter I recognizes 2.5 gallons of foam, 20 pounds of dry chemical, and 35 pounds of carbon dioxide as hand portable/semi-portable extinguishers suitable for Class B fires; therefore, all listed options meet the requirements.