The statement has a part missing. Choose the best option from the four options given below the statement to make up the missing part.
Archaeologists believe that the pieces of red-ware pottery excavated recently near Bhavnagar and ______ shed light on a hitherto dark $600$-year period in the Harappan history of Gujarat.
- estimated with a reasonable certainty as being about $3400$ years old,
- are estimated reasonably certain to be about $3400$ years old
- estimated at about $3400$ years old with reasonable certainty,
- with a reasonable certainty to be about $3400$ years old,