Question

Check each sentence that is true about molds and casts.
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Both molds and casts give a three-dimensional view of the organism.
A cast is a hollow area in sediment in the shape of the organism.
A mold forms when water seeps into the sediment and rots away the remains of the organism.
Molds and casts are the most common types of fossils.

Answer 1

True — Both molds and casts preserve the organism’s three‑dimensional shape (a mold is a hollow impression; a cast is a filled replica).

False — A cast is not hollow; a mold is the hollow area in the sediment. A cast forms when that hollow is later filled.

True — A mold forms when the organism’s hard parts decay or dissolve (often aided by water percolation), leaving a cavity in the sediment.

True — Molds and casts are among the most common types of fossils, especially for organisms with hard shells or skeletons.