Which of the following equipment can a 1A operator operate?

A 1A operator has the qualifications to operate all tower cranes, guy derricks, and Chicago booms due to the comprehensive skill set and training that comes with this specific license. This level of certification is designed to encompass a wide range of crane operations, allowing the operator to manage various types of heavy equipment safely and effectively.

Operating tower cranes, for instance, requires a deep understanding of lifting capacities, rigging, and the mechanics involved in the crane's operation, all of which are taught as part of the training for a 1A license. Guy derricks and Chicago booms also involve sophisticated lifting and positioning techniques, which further necessitate the broad capabilities that a 1A certification ensures.

In contrast, the other options either limit the scope of operation or specify a narrower range of equipment. Only small mobile cranes, fixed hoists, and block systems do not reflect the full range of equipment that a 1A operator is trained to handle. Moreover, specifying hydraulic equipment with a load capacity of 10 tons restricts the variety of equipment a 1A operator can manage, which is not representative of the qualification standards. Hence, option A accurately encapsulates the full capabilities of a 1A hoisting license.