NP126 missing using statements in “Add Reference…”

Hi Guys

NP126 missing using statements in “Add Reference…”

Though following using statements are in VS IDE Form designing code some using statements (highlighted in yellow) are missing in the “Add Reference…”. I wish to know the reason. Please explain the reason.

using System;

using System.Drawing;

using System.Collections;

using System.ComponentModel;

using System.Windows.Forms;

using System.Data;

Thank you