"I study" could be a response to a question such as "What do you do after class"
It is correct, because “to study” is an action verb, so the default aspect for the present tense is progressive in English, but indicative in Spanish. Please report it if it's not accepted.
It is often used when discussing college majors, like "I study english at Stanford" for example. I think it can be used for I am studying but more literally that would be Estoy estudiando.
There is no reason why "I am studying" is incorrect here, it does not mean "I am studying right now" as "estoy estudiando" would or "estoy estudiando ahora mismo" would but in context it works. "I am studying for my GCSE's this year" for example. I don't have a link unfortunately but Michel Thomas explains this very well. Please note that "I study" is also correct and does make sense in English contrary to some comments. eg "I study every day for two hours"
I can't hear "e" in "estudio". I was like "Yo studio". Is it normal? Because I know that sometimes vowels are omitted in spoken Spanish.
The ‘oe’ in ‘Yo estudio” form a diphthong. Perhaps you're listening for a break between the words, but there's no glottal stop in Spanish.
This should be - I'm studying.Or I am studying. I study don't make any sense, unless you are asked what do you do after class, or in the evening.
‘estudiar’ doesn't mean “to learn”. See the reply to mukaramn (Edit: now Pifta).
I don't see any mukaramn in here. If 'estudio' doesn't mean 'I learn' then the duolingo hover-answer is wrong, as it shows 'estudio' = (I) study, (I) consider, (I) learn.
spacec- the hints are not all correct answers, they're just related words. There's a small difference between study and learn. Ex : I tried to study Arabic but learned absolutely nothing.