Concept:The upper course of a river has a steep gradient and active downward erosion, forming features such as gorges and rapids.
Explanation:Deltas are deposited at the river's mouth, so they belong to the lower course.
Gorges are deep, narrow valleys created by strong vertical erosion in the upper course.
Meanders are gentle bends that develop mainly in the middle and lower courses.
Rapids form in the upper course where the river flows swiftly over hard, resistant rocks.
Therefore, the features linked with the upper course are gorges and rapids, which are II and IV.
Answer:D. II and IV