Answer: Alexei is a 6-month-old infant. When he cries in the middle of the night, one of his parents quickly comes to see what he needs. It is probably advisable that his parents continue to respond reliably, because Alexei is in Erikson's Trust vs. Mistrust stage of development.
Explanation: Trust vs. Mistrust is the first stage of psychosocial development of Erikson. This stage extends from the moment in which the child is born until he/she is one year old. Moreover, it is considered to be the most important stage in life since it is during this stage that children develop their own sense of trust, which depends exclusively on how much love and care they receive from their parents. In that way, Alexei is in the Trust vs. Mistrust stage of development because he is only 6 months old and he needs his parents to show love for him. Moreover, Alexei's parents must satisfy Alexei's most basic needs in order for him to develop trust.