In the question we have to use first projection operation , then Natural join and after that division operator on them.
1st step:
From project table with P_No as primary key we get project number of all employees by using ∏ p_no (Project)
2nd step:
Now from Employee ⋈ (Assigned_To) using natural join on Employee and Assigned_To table gives us emp no , emp name and project number of all employees.
3rd step:
After that we use division operator ÷ , on the tuples of two tables which we get from step 1 and step 2 , which gives details of all the employees who are working on all the projects. So this step gives employee details based on their Project _No which we get from step 1 .
Thus that given relational algebra represents this sentence :
List details of the employees working on all the projects. Which is option D .