Final answer:
The migration pattern described where migrants achieve long-distance goals in small steps is called step migration, which falls under the category of incremental migration. The correct answer to the student's question is a. Incremental migration.
Step-by-step explanation:
The migration pattern where migrants travel short distances and move in steps, slowly achieving long-distance goals, is called step migration, which is a type of incremental migration. This process involves migrants moving through a series of locations, often from rural to urban areas, with each move getting them closer to their final destination. This may occur due to various factors, such as economic opportunities, seasonal labor needs, or external pressures like political violence or natural disasters.
Incremental migration contrasts with rapid migration, where individuals move quickly and directly to their final destination, and reverse migration, where individuals return to their place of origin. Therefore, the correct answer to the question is a. Incremental migration.