Explanation:

Box model:

Each HTML elements is considered as “boxes”. In Cascading Style Sheet, the word box model is used while discussing about design and layout.

It is basically a box, which wraps every element in a document; the components of the box model from outermost to innermost are:

• Margin
• Border
• Padding
• Content

Margin:

Margin is one of the components of box model. It defines an empty space between an element and any adjacent elements.

It is always transparent; hence the page background color or parent element shows in this area.

Border:

The border is an area between the content and the margin areas. The value of the default border is “0” that does not displayed on the page.

• Using “border property”, user can configure an element’s border.

Content:

It is an area, contains a combination of both text and HTML elements such as headings, images, list and so on.

It does not contain any other components like margin, border and padding.

Padding:

The padding is an area between the content and the border areas. The default value of padding is “0”.

Using “padding property”, user can configure an element’s padding.

Explanation for incorrect options:

b)

The given listed components are from innermost to outermost of the box model.

Hence, the option “B” is wrong.

c)

The given listed components are not from the outermost to innermost of the box model. The correct components are margin, border, padding and content.

Hence, the option “C” is wrong.

d)

The given listed components are not from the outermost to innermost of the box model. The correct components are margin, border, padding and content.

Hence, the option “D” is wrong.