Answer
The hypothesis formulated would be: The presence of a pebble of basalt, an igneous rock, within a sedimentary rock, can be explained by the process of sedimentary rock formation involving the concepts of sedimentary recycling or reworking.
Work Step by Step
In order to investigate his hypothesis further one can:
conduct fieldwork in the area where the sedimentary rock containing the basalt pebble is found.
Collect detailed information about the rock layers, their composition, and their spatial distribution.
Identify any geological features or events that may have influenced the sedimentary deposition and subsequent incorporation of the basalt pebble.