a$.$ Technical skill: This refers to the proficiency in a specific field or discipline. While Lionel may possess technical skills related to engineering, the emphasis in the scenario is on his ability to create strategies, which falls more under conceptual skill.

b$.$ Human skill: Human skill involves the ability to work well with others and build positive relationships. While Lionel is mentioned to work well with his employees and has built a positive rapport, the primary focus in the scenario is on his strategic thinking and problem$-$solving abilities.

c$.$ Behavioral skill: Behavioral skills typically refer to interpersonal and communication skills. While Lionel's positive rapport with employees involves behavioral skills to some extent, the main highlight in the scenario is his strategic thinking, which aligns more with conceptual skill.

d$.$ Conceptual skill: As mentioned earlier, this skill involves the ability to analyze complex situations, understand the organization as a whole, and develop strategic solutions. Lionel's proficiency in creating strategies for organizational problems aligns with conceptual skill.