弱弱問GWD-TN-21 Q28

Rock samples taken from the remains of an asteroid about twice the size of the 6-nuke-wide asteroid that eradicated the dinosaurs has been dated to be 3.47 billion years old and thus is evidence of the earliest known asteroid impact on Earth.

1. has been dated to be 3.47 billion years old and thus is

2. has been dated at 3.47 billion years old and thus

3. have been dated to be 3.47billion years old and thus are

4. have been dated as being 3.47 billion years old and thus

5. have been dated at 3.47 billion years old and thus are

OG12最后一题，GMAC的官方解释是：The idiomatic way of expressing estimation of age is with the phrase 'dated at'