During substrate level phosphorylation, ATP synthesis is by:

(a) ATP synthase  
(b) ATPase
(c) Kinase                      

During substrate level phosphorylation, ATP synthesis is by Kinase.

Substrate-level phosphorylation is a direct method of ATP synthesis during cellular metabolism. In this process, a phosphate group (Pi) is transferred from a high-energy substrate molecule to ADP (adenosine diphosphate) to form ATP (adenosine triphosphate). This reaction is catalyzed by enzymes called kinases.