Final answer:
Calcium phosphate stones are associated with alkaline urine.
Step-by-step explanation:
Calcium phosphate stones are associated with conditions such as hyperparathyroidism and renal tubular acidosis. They are not specifically associated with being mixed with struvite or oxalate stones. However, they can form in alkaline urine, making choice a. Associated with alkaline urine the correct characteristic associated with calcium phosphate calculi.