Final answer:
Cancer-causing Rb mutations are loss-of-function and recessive, meaning both alleles need to be mutated for cancerous growth, therefore the correct answer is B) Loss-of-function, recessive.
Step-by-step explanation:
Cancer-causing Rb mutations in the retinoblastoma gene are typically loss-of-function and can be considered recessive when referring to their effects on the cellular level. These Rb mutations can lead to cancer because they inactivate the function of tumor suppressor genes which normally help to control cell growth and prevent tumor formation. The correct choice, therefore, is B) Loss-of-function, recessive. While some mutations may exhibit a dominant negative effect, causing a mutated product to interfere with the wild-type allele, this is generally not the case with Rb mutations. Instead, both alleles need to be mutated for the loss of function in Rb to trigger cancerous growth, reflecting a recessive pattern.