DIAGNOSIS Those black streaks are usually caused by dirt or dried ink on the scanner glass or, more specifically, on the white plastic strip underneath the scanner lid (the backing strip).
FIX For copies and scans, the problem is in the scanner assembly, not the printer. Lift the scanner lid. You'll see two pieces: the flat glass bed and the white plastic backing on the underside of the lid. That white plastic gets dirty. Take a soft, lint-free cloth slightly dampened with water or glass cleaner, and thoroughly wipe down the entire flatbed glass. Then, carefully clean that white plastic strip on the lid. Dry everything completely with a dry part of the cloth before closing the lid and trying another copy.
IF THAT DIDN'T WORK If the streaks are only on printed pages (not copies), then the issue is with the printer, not the scanner. That points to a dirty print head or a problem with the black ink cartridge. Run a Print Head Cleaning cycle from the Maintenance menu, followed by a nozzle check pattern.
HEADS UP Never use abrasive cleaners or paper towels on the scanner glass—they scratch it. Those scratches will then appear as permanent lines on every single copy and scan you make.