Adventive embryony in Citrus is due to

Options

A. egg
B. nucellus
C. embryo
D. integument

Explanation

### Step-by-Step Solution

1. **Understanding Adventive Embryony**:
- Adventive embryony refers to the formation of embryos from tissues other than the zygote. In this case, it occurs in the citrus plant.

2. **Identifying the Source of Embryo Formation**:
- In citrus, the additional embryos are formed from the nucellus, which is a tissue within the ovule. The nucellus is diploid and can give rise to embryos without fertilization.

3. **Distinguishing Between Different Structures**:
- The egg (option A) is formed through fertilization and is not involved in adventive embryony.
- The embryo (option C) is the result of fertilization and differentiation of the zygote, thus also not applicable.
- The integument (option D) is protective tissue around the ovule and does not contribute to adventive embryony in this context.

4. **Correct Answer Identification**:
- The correct option is B, which states that adventive embryony in citrus is due to the nucellus. This is because the nucellus can produce embryos that are genetically identical to the parent plant without the need for fertilization.