： ‌The positioning of the dorso-ventral axis in Xenopus is deter mined by (   ), while the positioning of the antero-posterior axis in chicks is deternined by (   ).‏A: gravity; point of sperm entry B: maternal factors in both cases C: position in the egg chamber; gravity D: the point of sperm entry; gravity 答案:  the point of sperm entry; gravity