What is the primary method of direct fire?

The primary method of direct fire in artillery is accomplished through the use of the M119A3Howitzer, which is specifically designed for such engagements. Among the choices provided, the M90A3 is the correct answer because it represents the artillery system that is optimized for direct fire applications. This method involves firing rounds directly at a target and requires accurate aiming and positioning to achieve effective results.

The M119A3 Howitzer is capable of delivering precise artillery support in a direct fire role, especially in close combat situations where indirect fire might not be suitable. Its design incorporates features that enhance accuracy and reduce collateral damage, making it ideal for direct engagements with enemy forces or equipment.

The other models listed, such as the M137A2, M1A2, and M137A1, may serve different roles or represent alternative equipment not primarily associated with direct fire capabilities in the same context as the M90A3. Therefore, the choice of M90A3 as the primary method of direct fire aligns with the specific operational requirements of artillery units engaging targets in a direct method.