Final answer:
Josefina is likely struggling with 8th-grade chemistry because of inadequate exposure to abstract reasoning tasks, as per Piaget's formal operational stage of cognitive development.
Step-by-step explanation:
According to Piaget's Theory of Cognitive Development, Josefina is most likely struggling with 8th-grade chemistry concepts due to Inadequate exposure to abstract reasoning tasks (c). Piaget's formal operational stage, which starts around age 11, encompasses the ability to think abstractly and to understand hypothetical situations, both of which are required for mastering chemistry concepts. Given the typical age for 8th-grade students, it is expected that Josefina should be able to handle such reasoning; however, if she has not had sufficient exposure and practice with abstract reasoning, she may find the concepts in chemistry challenging.
Factors like lack of concrete operational thinking (a) are less likely since, by 8th grade, Josefina would have passed the age where concrete operational skills are typically developed (7 to 11 years old). Similarly, difficulties due to underdeveloped sensory-motor skills (d) are unlikely as these skills are developed in the first stage of Piaget's theory, which ends around age 2. Furthermore, while insufficient social interaction (b) can impact learning, it is not directly related to the struggle with abstract concepts as per Piaget's stages.