Answer:
А. adulthood
Step-by-step explanation:
"Intimacy vs. Isolation" is common in the young adults (adulthood). This age ranges from 20s until the early 40s. It is very important for a person to develop a positive self-concept in order not to feel isolated when it comes to his/her emotions. This makes choice A correct.
"Middle adulthood" is under "Generativity vs. Stagnation" stage, so this makes choice B incorrect.
"Late adulthood" is under "Integrity vs. Despair" stage, so this makes choice C incorrect.
"Adolescence" is under "Identity vs. Role Confusion" stage, so this makes choice D incorrect.