**Core Concept**
In vitro fertilization (IVF) and embryo transfer (ET) are reproductive technologies used to treat infertility in individuals or couples. IVF involves fertilizing an egg with sperm outside the body, and ET involves transferring the resulting embryo to the uterus.

**Why the Correct Answer is Right**
IVF and ET are used to treat various indications such as:
- **Option C:** Tubal blockage or damage, which prevents natural fertilization. IVF bypasses the damaged tubes and allows fertilization to occur outside the body.
- **Option D:** Unexplained infertility, where couples have tried other treatments but have not conceived. IVF is often a last resort for these couples.

**Why Each Wrong Option is Incorrect**
* **Option A:** While age is a factor in fertility, IVF is not exclusively indicated for older women. IVF can be used for women of any age who are experiencing infertility.
* **Option B:** Low sperm count or poor sperm quality can be treated with intrauterine insemination (IUI) or IVF, but it's not an absolute contraindication for IVF.

**Clinical Pearl / High-Yield Fact**
IVF can be used for a wide range of indications, including tubal blockage, unexplained infertility, and low sperm count. However, it's essential to consider other factors such as age, ovarian reserve, and uterine receptivity before recommending IVF.

**Correct Answer: B. Low sperm count is not an absolute contraindication for IVF.**