In Holmes' convection idea, which surface feature is more likely to form above a rising current?

Correct answer: Ridge or rift zone

The direct answer is D, a ridge or rift zone. In Holmes’ convection idea, hot material rises from inside Earth while cooler material sinks. Where a hot rising current reaches the crust, it can push the crust upward and apart. Such divergence may produce a mid-oceanic ridge or a continental rift. The reasoning is: rising hot current → upward pressure and stretching → crustal separation → ridge or rift. Option A, a deep oceanic trench, is generally associated with convergence and the sinking of one plate beneath another, not with rising material. Option B, a convergent mountain belt, forms mainly when plates move toward each other and compress the crust; it is the opposite movement. Option C, an abandoned river valley, is produced by river processes and has no necessary link with mantle convection. Option D is correct because a rising current is associated with divergence, spreading and elevated crust. Memory cue: rising current spreads the crust; spreading makes a ridge or rift.