IUDs which are used by females :

Options

A. act as spermicidal jellies
B. block the entry of sperms into vagina
C. implanted under the skin and they release progesterone and oestrogen
D. release copper ions in the uterus that increase phagocytosis of sperms

Answer

**Step-by-Step Solution:**

1. **Understanding IUDs**: Begin by defining what IUDs (Intrauterine Devices) are. They are contraceptive devices inserted into the uterus to prevent pregnancy.

2. **Analyzing the Options**:
- **Option 1**: "Act as spermicidal jellies." This is incorrect because IUDs do not function like spermicidal jellies, which kill sperm. Instead, IUDs work differently.
- **Option 2**: "Block the entry of sperms into vagina." This option is also incorrect. IUDs do not block sperm entry; they work within the uterus after sperm have entered.
- **Option 3**: "Implanted under the skin and they release progesterone and estrogen." This is not correct as it describes hormonal implants, not IUDs.
- **Option 4**: "Release copper ions into the uterus that increase phagocytosis of sperms." This is the correct option. IUDs, particularly copper IUDs, release copper ions which help in inactivating sperm.

3. **Conclusion**: Based on the analysis, the correct answer is that IUDs release copper ions into the uterus, which increases the phagocytosis of sperm, effectively preventing fertilization.

**Final Answer**: IUDs used by females release copper ions into the uterus that increase phagocytosis of sperms.

---