Differentiation occurs when: the sperm and ovum meet. cells begin to specialize. the combined material from both gametes meshes together. the zygote reaches the four-cell stage.

The correct answer is option - cells begin to specialize.

Explanation:

Embryonic differentiation is a process in which the cell begins to divide and to be destined to make a specific cell line different from another cell. Each differentiated cell has fate to perform a specific function in later development in the body.

The embryonic cell differentiation takes place when the cell begins to specialize which is occurs after the cleavage of a zygote which triggers the differentiation process.

Thus, the correct answer is option - cells begin to specialize.

the second type of galaxy is called a barred spiral, which has a thing called a bar straddling the nucleus

events in order:

1.       vishnu schist

2. zoroaster granite

3. bass limestone

4. hakatar   shale

5. igneous intrusion

6. shinumo quartzite

7. dox sandstone

8. tapeats limestone

9. bright angel shale

10. muav limestone

11. temple butte limestone

12. redwall limestone  

nonconformity

answer: the unkar group shows angular unconformity because the layers are turned at angle.

unconformity

answer: specifically the angular unconformity occurs between the cambrian and precambrian rocks. the dox sandstone, shinumo quartzite, hakatar shale, and bass limestone have been filled. an angular unconformity occurs between the cambrian and precambrian rocks. the dox sandstone, shinumo quartzite, hakatar shale, and bass limestone have been filled.

disconformity

answer: the disconformities aremarked irregular lines between the sedimentaryrocks layers.