When archaeologists excavate a site, they always

a. nonintrusive techniques like ground-penetrating radar and sonar to avoid destruction.

b. excavate as much as they can of a site to try to record as much of the context of the artifacts as possible.

c. refill the site with the unimportant artifacts when they are finished, since they may be of value later.

d. excavate a small part of a site to preserve the site for future archaeologists.