Final answer:
The exact reason Richard hid his marriage plans is not provided, but it could be influenced by common royal political concerns such as betrayal, conflict, secrecy, or backlash.
Step-by-step explanation:
The reason Richard hid his plan to marry Berengaria of Navarre from Philip is not explicitly mentioned in the materials provided, and without more context, it is challenging to determine the exact motive. However, if we reflect on the historical relationships and dynamics between royal families and their political ties, it is reasonable to speculate that reasons such as fear of betrayal (A), avoidance of conflict (B), desire for secrecy (C), or to prevent political backlash (D) could have played a role in Richard's decision to keep the marriage plans concealed from Philip. Any of these reasons would be based on the political and personal intricacies of monarchal alliances and hostilities at that time