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: Understand Availability 
Availability refers to the potential to do useful work from a system. It depends on the system's state and environment. 
Step 2: Analyze each statement - (A) Availability is generally conserved: Availability is not generally conserved in real processes due to irreversibilities (like friction, heat loss, etc.), so this is false.
- (B) Availability can neither be negative nor positive: This is incorrect, because availability can be positive (if the system can do useful work) or negative (if the system is in a state where it cannot do any work).
- (C) Availability is the maximum theoretical work obtainable: This is true, as availability is the maximum work that can be obtained in a given process.
- (D) Availability can be destroyed in irreversibilities: This is correct, as irreversible processes (e.g., friction, mixing, heat transfer) reduce the availability of a system.
Step 3: Conclusion The correct statements are (C) and (D), so the answer is (4). 
Final Answer: \[ \boxed{(C) \, \text{and} \, (D) \, \text{only}} \]