The phrase "a complex question that" is correct and usable in written English.
It can be used when introducing a question that has multiple layers or requires deep thought to answer.
Example: "The researcher posed a complex question that challenged the assumptions of the existing theories."
Alternatives: "a multifaceted question that" or "a challenging question that".
That's a complex question that deserves a separate blog post.
Why France should have proved more welcoming to black people than America or Britain is a complex question that necessitates an examination of its ultural and moral attitude towards them in history.
The IRS admission comes amid a debate about when political groups on both sides deserve tax-exempt status — a complex question that turns on whether the group is working mainly to support a general philosophy or a specific party or candidate.
This appears to be a complex question that will be the subject of future work.
It is quite a complex question that is beyond the scope of this paper.
But for many bereaved parents, it can be a complex question that gets a different answer depending on who is asking and where we are.
This is a more complex question that depends on the situation.
The native range points cover the full known geographic range of the species, based on the best available botanical description [47]; however, whether they cover the full environmental range is a much more complex question that has not been examined in this contribution.
While this is an excellent example of lack of transfer, why students were unable to make the connection from the first to the second demonstration is an interesting and complex question that remains unresolved.
In a report accompanying the resolution, the executive committee said the bill was a hasty and "inappropriate response to a highly complex question" that Congress should not address without holding hearings and inviting public participation.
Of course, the influence on the Australian economy of the aggregate scale of the skilled migrant intake is a more complex question that our analysis does not touch upon and which remains for further research.
