Consider the given statements.
I. Proliferative phase is caused by the increased production of oestrogens.
II. During luteal phase endometrium thickness increases upto 10 mm.
III. Menstrual flow includes blood only.
IV. During ovulatory phase primary oocyte is released.
Choose the correct statements.

Options

A. I and II
B. I and III
C. II and III
D. III and IV

Answer

To solve the question regarding the correctness of the given statements about human reproduction, we will evaluate each statement one by one.

### Step-by-Step Solution:

1. **Evaluate Statement I**: "Proliferative phase is caused by the increased production of oestrogens."
- The proliferative phase of the menstrual cycle is indeed stimulated by the increased levels of oestrogens produced by the developing follicles. Therefore, this statement is **correct**.

2. **Evaluate Statement II**: "During luteal phase endometrium thickness increases up to 10 mm."
- During the luteal phase, the hormone progesterone is secreted, which promotes the thickening and maintenance of the endometrium. It is common for the endometrium to reach a thickness of about 10 mm during this phase. Thus, this statement is also **correct**.

3. **Evaluate Statement III**: "Menstrual flow includes blood only."
- Menstrual flow does not consist of blood alone; it also includes endometrial tissue, mucus, and other fluids. Therefore, this statement is **incorrect**.

4. **Evaluate Statement IV**: "During ovulatory phase primary oocyte is released."
- During ovulation, it is the secondary oocyte that is released, not the primary oocyte. The primary oocyte completes its first meiotic division just before ovulation. Hence, this statement is **incorrect**.

### Conclusion:
The correct statements are:
- Statement I: Correct
- Statement II: Correct
- Statement III: Incorrect
- Statement IV: Incorrect

Thus, the correct answer is that **Statements I and II are correct**.