What protects bones from hitting each other?

What should be changed to make the following sentence true? "the stress model suggests that people with a predisposition for a disorder are more likely to develop the disorder when faced with stress."

Avirus consisting of a single strand of rna, which is transcribed into complementary dna, is a ) proteaseb) retrovirusc) rna replicase virusd) nonenveloped virus

According to bowlby which of the following is not required in order for infants to form healthy attachments with their parents