The best answer to the question states above is letter C.<span> A short observation period. </span>
<span> A scientist's primary concern in a clinical trial is the patient's safety, there fore short observation </span><span>decreases the reliability of results from a clinical trial</span>
Sandstone contains fossils of creatures such as trilobites, brachiopods, crustaceans, bryozoans and plants. Remains of land animals like mastodons and dinosaurs are much more likely to be found in sandstone.
