Malthus' contention is that

Thomas Robert Malthus, in his 1798 work An Essay on the Principle of Population, argued that population increases in geometric progression (i.e., it multiplies: 2, 4, 8, 16, 32, ...) while food production increases only in arithmetic progression (i.e., it adds a constant amount: 1, 2, 3, 4, 5, ...).

Because a geometric series grows much faster than an arithmetic series, Malthus concluded that population would inevitably outstrip the food supply unless checked by what he called positive checks (famine, disease, war) or preventive checks (moral restraint such as delayed marriage).

The option stating the reverse, that population grows arithmetically while food grows geometrically, directly contradicts Malthus's theory. The option suggesting the two will be at par in the future is also incorrect because Malthus's central point was that they would diverge, not converge. The option about nations needing manpower to cultivate land describes a general statement about agricultural labour, not the specific population-food growth relationship Malthus proposed.