Final answer:
Juliet is concerned about Romeo being present in the tomb where she lies, fearing it may lead to tragic consequences. Romeo responds by expressing his love for Juliet and his intention to join her in death.
Step-by-step explanation:
Juliet's concern about Romeo being present is rooted in the fact that he has come to the tomb where she lies, mistakenly believing she is dead. She fears that he will find her lifeless body and feel extreme despair, leading him to possibly harm himself. Her concern is that Romeo's presence in the tomb may lead to tragic consequences.
Romeo responds to Juliet's concerns by expressing his deep love for her and his intention to join her in death. He refuses to leave the tomb and insists on staying by her side, stating that he would rather die with her than live without her.