"I must research the features of this material."
Translation:Bu maddenin özellikleri hakkında araştırma yapmalıyım.
If your question is: why is the accusative case not used? --
"Bu maddenin özellikleri" is not the direct object of the verb yapmak, it is the complement of the post-position hakkında. (The d.o. seems like it would be araştırma, but I suspect that araştırma yapmak is treated more like a compound verb.) As someone noted earlier, if you use the verb araştırmak instead, then "bu maddenin özelliklerini" would be correct, because it is the specific direct object of that verb.
Bu maddenin özellikleri hakkında araştırma yapmalıyım.
Bu maddenin özelliklerini araştırmalıyım.
Is there some reason why yapmam lazim cannot be accepted instead of yapmaliyim? (Sorry, no Turkish keyboard). From what I have read so far in the course, any of the following should be acceptable:
Yapmaliyim Yapmam lazim (or gerekiyor) Yapmak zorundayim
Am I wrong about this? In many questions, Duo accepts one of these but not the others. Is there a difference? I have put this question on many pages but get no responses.
Myself a learner I will try to give you an answer as far as possible.
The sentence in question says: " ... must ... ". 'Must' is stronger than 'need to'. They do not express the same thing so they should normally not be translated the same way.
lazım / gerekiyor = need to
-malıyım / -meliyim = should (have to / must)
zorunda = have to / must
(to the best of my knowledge)
Since reading your response, I have been translating Duo questions that use need to with gerekiyor and those that use have to/must with zorunda and my answers are accepted as correct every time. Clearly your explanation is correct, and I am very grateful for it. However, all my life I have been using "need to" and "have to" interchangeably (and therefore probably wrongly). Could you give me your view on the difference between "I need to eat" and "I have to eat", perhaps by giving situations when each might be used?