Final answer:
Biologically, the female in humans has a greater investment in producing offspring due to the demands of gestation, lactation, and associated risks. In species with long-term parental care, fewer offspring are produced, signifying a higher investment in each child. The greater biological investment, in this case, is on the female's part.
Step-by-step explanation:
Parental Investment Theory in Biology
In terms of biological investment, it is generally understood that in humans, the female has a greater investment in producing offspring. This is because the biological contributions, such as gestation and lactation, are considerable in terms of time, energy, and resources. Additionally, the risks associated with pregnancy and childbirth mainly fall on the female. Therefore, from a strictly biological standpoint, mothers tend to invest more in having a baby.
Moreover, organisms that invest in long-term parental care, such as humans, tend to have fewer offspring. This strategy means that there is a higher investment in each individual offspring, which can translate to a greater chance of survival for those offspring but at a greater risk to the survival of the species if a single offspring dies, as stated in option b. This contrasts with species that produce many offspring with less parental investment, where the survival of an individual offspring is less critical to the survival of the species.
While parental investment in humans involves more than biology, such as emotional and financial support, answering this question in the context of biology alone highlights the mother's greater biological investment in the process of having a baby.