If microwaves, X-rays, infrared, gamma rays, ultraviolet, radio waves and visible parts of the electromagnetic spectrum are denoted respectively by M, X, I, G, U, R and V the following is the arrangement in ascending order of the wavelength:

To solve this problem, we need to arrange the given parts of the electromagnetic spectrum in ascending order of wavelength, meaning from the shortest wavelength to the longest wavelength. The notations provided are: Microwaves (M), X-rays (X), Infrared (I), Gamma rays (G), Ultraviolet (U), Radio waves (R), and Visible light (V).

First, recall the order of the electromagnetic spectrum based on wavelength. The electromagnetic spectrum is typically ordered from the shortest wavelength (highest energy) to the longest wavelength (lowest energy) as follows: Gamma rays, X-rays, Ultraviolet, Visible light, Infrared, Microwaves, Radio waves.

Now, let's map this order to the given notations:

• Gamma rays are denoted by G.
• X-rays are denoted by X.
• Ultraviolet is denoted by U.
• Visible light is denoted by V.
• Infrared is denoted by I.
• Microwaves are denoted by M.
• Radio waves are denoted by R.

Therefore, arranging them in ascending order of wavelength (shortest to longest):

1. Gamma rays (G) - shortest wavelength
2. X-rays (X)
3. Ultraviolet (U)
4. Visible light (V)
5. Infrared (I)
6. Microwaves (M)
7. Radio waves (R) - longest wavelength

So the sequence is: G, X, U, V, I, M, R.

Now, compare this sequence with the given options:

• Option A: I, M, R, U, V, X, G → This starts with Infrared (I), which is not the shortest wavelength. Incorrect.
• Option B: R, M, I, V, U, X, G → This starts with Radio waves (R), which has the longest wavelength, so it is descending, not ascending. Incorrect.
• Option C: M, R, V, X, U, G, I → This starts with Microwaves (M), which is not the shortest wavelength. Incorrect.
• Option D: G, X, U, V, I, M, R → This matches our sequence: Gamma (G), X-rays (X), Ultraviolet (U), Visible (V), Infrared (I), Microwaves (M), Radio (R). Correct.

Hence, the correct answer is Option D.