Match the description of these XBRL terms with their descriptions.
Source: http://www.ge.com/annual01/letter/cockpit/.
1. A document containing XBRL elements.
2. Adds presentation elements to XBRL instance documents to make them more readable to people.
3. Defines and describes each key data element (e.g., total assets, accounts payable, net income, etc.).
4. Provides the underlying technical details of what XBRL is and how it works.

A. XBRL instance document
B. XBRL specification
C. XBRL style sheet
D. XBRL taxonomy