"Climate Action Tracker", which monitors the emission reduction pledges of different countries is a:

(a) Correct. Climate Action Tracker (CAT) is an independent scientific analysis/database produced by a coalition of research organisations such as Climate Analytics and NewClimate Institute.
(b) Incorrect. It is not a wing of the IPCC; the IPCC assesses climate science, while CAT tracks countries’ pledges and actions.
(c) Incorrect. It is not a committee under the UNFCCC; CAT is an independent initiative outside the formal UNFCCC structure.
(d) Incorrect. It is not an agency financed/promoted by UNEP and the World Bank. CAT is run by independent research organisations, not as a UN–World Bank body.