Final answer:
The allies stalled the Central Powers by destroying German warships, severing trade links, and using troops from their colonies.
Step-by-step explanation:
The correct answer is d. All of these. By the beginning of 1915, the allies stalled the Central Powers by using a combination of strategies. They destroyed German warships that were navigating outside the North Sea, severing Germany's and Austria's overseas trade links. Additionally, they utilized troops from their colonies to bolster their forces and put pressure on the Central Powers.
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