Answer choices are:
A. Slab pull and crust conversion 
B. Plate movement and convection currents 
C. Connection and convection 
D. Ridge push and slab pull
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Correct answer choice is:
D. Ridge push and slab pull
Explanation:
Ridge Push: The process that occurs when magma arises at a mid-ocean ridge and drives oceanic plates in two separate ways apart from the ridge. 
Slab pull: The process that occurs if a thick oceanic plate settles underneath a more resilient plate with a subduction zone, drawing the excess of the plate that pursues following it.