他从小就感受到一种强烈的使命感要成为一名教师。

He felt a strong ___calling to become a teacher since childhood.

她选择成为一名医生，因为她觉得这是她真正的使命。

She chose to be a doctor because she felt it was her true ___calling.

她感受到了一种强烈的召唤，决定成为一名修女。

She felt a strong ___calling and decided to become a nun.