"Themanhasthebook."

I'm a native English speaker. The word "book" is definitely in the sentence audio and it is clear that the word "book" is being said. However, remember that Duolingo uses a robot voice which often doesn't sound completely natural. In this sentence the word "book" does sound a bit funny and robotic. This is something that you will get more used to as you use Duolingo more and more. You can hear the word book pronounced in many different English accents from around the word here.

No, that is not correct. Please read this comment here for more detail https://www.duolingo.com/comment/2818055. The verb "to have" is a bit different - we say "The man has" and not "The man haves" but otherwise the rule follows the same pattern:

• I have
• You have
• He has
• She has
• It has
• They have
• The man has
• The men have

'has' is used with singular subject. Here, man is a singular subject, so we will use 'has'. But remember the exceptions - 'I' and 'You'. We do not use - 'I has a book' nor 'You has a book' although both 'I' and 'You' are singular subjects.

'has' का उपयोग एकवचन कर्ता के साथ किया जाता है. लेकिन 'I' और 'You' इस नियम के अपवाद हैं. चूँकि man एकवचन कर्ता है इसलिए हम The man has a book लिखेंगे. 'men' बहुवचन कर्ता है इसलिए हम The men have a book लिखेंगे.

I have a book. She/He has a book. You have a book.