Answer: b - Chondroblasts within the cartilage divide and secrete new matrix
Explanation: Chondroblasts are derived from two sources; mesenchymal cells within the center of chondrification and chondrogenic cells of the inner cellular layer of the perichondrium (coverings that lie over most cartilage).
At the chondrification centers, the cartilage forming cells (Chondroblasts) begin to secrete the components of extracellular matrix of cartilage. As the amount of matrix increases, the Chondroblasts become separated from each other and they are located in small cavity within the matrix called lacunae.
Concurrently, the cells differentiate into matured cartilage cells called chondrocytes.
One problem with this hypothesis is that the student didn't write about why this hypothesis might work - what is the underlying mechanism. The thing is that one might want to write the underlying mechanism or explanation in his hypothesis. Another problem with this hypothesis is that it's very hard to measure and be sure that following exposure to white chocolate, people are happier and that it's not a consequence of something else.
Yes, waves can carry energy through