"makes it questionable" is correct and can be used in written English.
You can use it to describe something that casts doubt on the truth or accuracy of a statement. For example: "The lack of evidence to support his claim makes it questionable whether the theory is correct."
He added, "The fact that it is so inflammatory makes it questionable.
Because the identification of welfare with preference satisfaction makes it questionable whether one can make interpersonal welfare comparisons, few economists defend a utilitarian view of policy as maximizing total or average welfare.
Importantly, research shows that people are fairly limited in their ability to predict their future behavior, which makes it questionable whether self-reported intentions are valid proxies of real-world behavior, especially in situations that are uncommon or situations that regard unconventional behavior (Exum & Bouffard, [2010]).
However, whole-genome sequences of appropriately positioned insect species to allow such an approach are not currently available, and the rapid radiation of the Insecta makes it questionable whether such intermediate species could be found.
Lack of the full complement of NADH dehydrogenase subunits and ATP synthase peptides makes it questionable as to whether the electron transport pathway is efficient for the generation of ATP from the products of glycolysis.
As such, the fact that absolute ultrafiltered volumes were comparable in both the less and more intensive patient groups makes it questionable whether there really was a difference of dose in the study by Vesconi and colleagues.
But most were of the view that the volume of material included made it questionable whether the new curriculum would ever actually be taught in full to pupils.
However, OFDM has some important drawbacks that make it questionable for future wireless systems as 5G networks [2].
Cellino already has two criminal convictions, making it questionable whether he will pass the Football League's ownership test.
-Nearly 30 companies are developing thin-film modules based on CIGS or CIS compounds, making it questionable how many will survive the current economic climate.
However, the text is ambiguous, making it questionable that Henry ever matures.
