a) Item
b) Property
c) Value
d) URL

Answer: a
Explanation: The microdata model consists of groups of name-value pairs known as items. Each group is known as an item. Each item can have item types, a global identifier (if the vocabulary specified by the item types support global identifiers for items), and a list of name-value pairs. A Uniform Resource Locator, called URL, termed as web address and is used for a reference to a web resource for finding its location. Property is information about a particular id or else attribute.