Ultimate limit states deal with the safety of the structural member.

Ultimate limit states (ULS) refer to the maximum load or condition that a structure can withstand without failure or collapse. These limit states ensure the safety and structural integrity of the member under extreme loading conditions. Here is a detailed explanation of why option 'A' is the correct answer:

1. Safety of the structural member:
Ultimate limit states primarily focus on the safety aspect of the structural member. They consider the strength, stability, and load-carrying capacity of the member under the most severe and extreme conditions. The design of a structure should ensure that it can resist the maximum possible loads without any failure or collapse, thereby ensuring the safety of the occupants and users of the structure.

2. Serviceability of the structural member:
Serviceability limit states (SLS) address the functional and aesthetic aspects of the structure. These limit states deal with deflections, vibrations, cracking, and other factors that affect the performance and appearance of the member. Unlike ultimate limit states, serviceability limit states focus on meeting specific criteria related to user comfort, durability, and appearance.

3. Creep of the structural member:
Creep refers to the time-dependent deformation of a material under a constant load. While creep is a significant consideration in some engineering applications, it is not directly related to ultimate limit states. Creep is typically considered under long-term or sustained loading conditions and is more relevant to serviceability limit states.

4. Aesthetics of the structural member:
Aesthetics primarily deals with the visual appeal and appearance of the structure. Although aesthetics play an essential role in architectural design, they are not directly related to ultimate limit states. The focus of ultimate limit states is on the structural safety and performance of the member, rather than its visual appeal.

In conclusion, ultimate limit states primarily deal with the safety of the structural member. They ensure that the member can withstand extreme loads without failure or collapse. Serviceability limit states, creep, and aesthetics are important considerations in structural design but are not directly related to ultimate limit states.