Which ink does the Canon PIXMA MG7520 use?

The Canon PIXMA MG7520 (inkjet, 2014) uses PGI-250XL, CLI-251, PGI-250.

Compatible cartridges

CartridgeColorYieldPagesOEM priceCost/page
PGI-250XL black XL500 $22.00 4.4¢ OEM · AmazonCompatible
CLI-251 black standard349 $13.00 3.7¢ OEM · AmazonCompatible
PGI-250 black standard300 $16.00 5.3¢ OEM · AmazonCompatible
CLI-251 cyan standard298 $13.00 4.4¢ OEM · AmazonCompatible
CLI-251 gray standard780 $14.00 1.8¢ OEM · AmazonCompatible
CLI-251 magenta standard298 $13.00 4.4¢ OEM · AmazonCompatible
CLI-251 yellow standard298 $13.00 4.4¢ OEM · AmazonCompatible

XL/high-yield cartridges usually cost more upfront but lower the cost-per-page — better if you print often.