Question

Consider the following statements: 
(A) Availability is generally conserved. 
(B) Availability can neither be negative nor positive. 
(C) Availability is the maximum theoretical work obtainable. 
(D) Availability can be destroyed in irreversibility's.

• A. (A), and (B) only
• B. (A), and (C) only
• C. (B), and (D) only
• D. (C) and (D) only

Hint:

Availability can be destroyed in irreversibilities, and it represents the maximum work obtainable from a system.

Answer 1

The Correct Option is D

Step 1: Define Availability
Availability is a system's potential to perform useful work, contingent on its state and environment.
Step 2: Evaluate Each Statement - (A) Availability is generally conserved: Incorrect. Irreversibilities (friction, heat loss) cause availability to not be conserved.
- (B) Availability can be negative or positive: Incorrect. Availability can be positive (system can do work) or zero (system cannot do work), but not negative based on the original definition.
- (C) Availability is the maximum theoretical work obtainable: Correct. Availability represents the maximum achievable work in a process.
- (D) Availability can be destroyed in irreversibilities: Correct. Irreversible processes (friction, mixing, heat transfer) diminish a system's availability.
Step 3: Summarize Statements (C) and (D) are correct; therefore, the answer is (4).
Final Answer: \[ \boxed{(C) \, \text{and} \, (D) \, \text{only}} \]