Which of the following is produced when magnesium ribbon burns in the presence of air?

Correct option is C

The correct answer is (c) White powder of magnesium oxide.
Explanation: When magnesium ribbon burns in the presence of air, it reacts with the oxygen to form magnesium oxide (MgO). The reaction is as follows:
$$2Mg+O_2→2MgO_2$$​
The product formed is magnesium oxide (MgO), which is a white powder.
· The burning process produces a bright white flame, and the white powder formed is magnesium oxide.
Other Options: 

• Blue powder of magnesium oxide: Magnesium oxide is not blue; it is white in color.
  
• Magnesium carbonate: This compound forms when magnesium oxide reacts with carbon dioxide, but it is not produced during the direct burning of magnesium in air.
  
• Magnesium dioxide: This is not a valid compound produced in this reaction.