Sb-22 when must you maintain a proper lookout by sight and hearing?

According to navigation rules and regulations, you are expected to maintain a proper lookout by sight and hearing at all time. Concerning looking out, the law states that 'every vessel shall at all time maintain a proper look out by sight and hearing and as well as by all appropriate means available in order to avoid the risk of collision'.   

The answer is b. amino acids sequences of human proteins