Explanation:
Cyclic loading refers to the repeated application of loads on a material. Under cyclic loading conditions, the stress concentration is more serious in ductile materials. This is because of the following reasons:

1. Strain hardening: Ductile materials like steel undergo strain hardening when subjected to cyclic loading. This means that the material gets harder and stronger as it is deformed repeatedly. As a result, the stress concentration at any given point in the material increases with each cycle of loading.

2. Fatigue failure: Ductile materials are prone to fatigue failure under cyclic loading conditions. This is because of the accumulation of microcracks in the material due to repeated loading. These microcracks can coalesce and grow into macrocracks, which can eventually lead to failure of the material.

3. Plastic deformation: Ductile materials undergo plastic deformation under cyclic loading conditions. This means that the material deforms permanently even when the load is removed. As a result, the stress concentration at any given point in the material increases with each cycle of loading.

In contrast, brittle materials like ceramics and glass are less prone to stress concentration under cyclic loading conditions because they do not undergo significant plastic deformation. However, they are more prone to sudden failure under cyclic loading conditions because they do not undergo strain hardening and are more brittle.

Conclusion:
In conclusion, stress concentration is more serious in ductile materials under cyclic loading conditions because of strain hardening, fatigue failure, and plastic deformation.

Correct answer is a) brittle as well as ductile materials.