In a period, the first ionisation enthalpy of the element at extreme left and the negative electron gain enthalpy of the extreme right element, except noble gases, are respectively.

In a period, the first ionisation enthalpy of the element at the extreme left and the negative electron gain enthalpy of the extreme right element, except noble gases, Lowest and Highest respectively.

For,

Extreme Left Element (Alkali Metals):
As we move from left to right across a period, atomic size decreases and the effective nuclear charge increases. 

Also, the element on the extreme left has the largest atomic radius in its period, making it very easy to remove its outermost electron. 

Thus, it possesses the lowest first ionisation enthalpy.

For,

Extreme Right Element, Except Noble Gases (Halogens):
Halogens require just one electron to complete their stable octet configuration. 

Because of their small atomic size and high effective nuclear charge, they release a tremendous amount of energy when gaining an electron. 

Thus, they have the highest negative electron gain enthalpy in the period.

Therefore, Option C is correct.