Is there any way to know the email id or to contact the person who had asked a question in yahoo answers?

There isn't any way to know their actual email address but........ You can email another user by clicking their avatar and see if they allow email or I.M and email them through answers if it shows Email (name) but if the link doesn't show they do not allow emails you can't email them.

>>>For you to send emails you have to allow them.

Click on the icon of that person and if he has shared his email id then you can contact the person directly otherwise not.

Click their avatar. If they allow contact, there will be links on that page to IM or email them privately. But many users don't allow it.

If the user allows people to contact them privately, then yes.

Yes

look at the profile of the person,

there you may find the link.

update1- 8 dec 2013.

funnily enough,you have not enabled the link.