The phrase "a challenging task that" is correct and usable in written English.
You can use it when describing a specific task that requires significant effort or skill to complete.
Example: "Completing the project on time was a challenging task that required teamwork and dedication."
Alternatives: "a difficult task that" or "a demanding task that".
Valuing the environmental impacts can be a challenging task that can also be quite time-consuming.
This is a challenging task that is rarely achieved through simple analysis of raw data alone.
Establishing security properties in a computer system is a challenging task that is often neglected during a system’s design.
Linking similar proteins structurally is a challenging task that may help in finding the novel members of a protein family.
From a pedagogical point of view, this situation represents a challenging task that requires new, innovative teaching methodologies.
Elucidation of protein protein interactions and networks is a challenging task that will require an integrated approach that combines different types of experiments in addition to bioinformatics analyses.
The separation of azeotropic mixtures is a challenging task that is currently performed by special distillation processes, such as heteroazeotropic, extractive or pressure-swing distillation.
Maintaining a comfortable indoor environment with minimum energy consumption is a challenging task that attracts the attention of experts around the world.
In contrast to digital designs, the verification of AMS systems is a challenging task that requires lots of expertise and deep understanding of their behavior.
The optimization of an organic Rankine cycle is a challenging task that cannot be tackled without the aid of numerical tools for plant simulation and optimization.
Visual Question Answering (VQA) is a challenging task that has received increasing attention from both the computer vision and the natural language processing communities.
