Is the osculum found in the ectoderm layer, the endoderm layer, or the mesoglea?

a chair, a bed, and a toothbrush

explanation:

i was told this before by a teacher, so yeah

the alkaline earth metals (beryllium (be), magnesium (mg), calcium (ca), strontium (sr), barium (ba), and radium (ra)) are a group of chemical elements in the s-block of the periodic table with very similar properties: shiny. silvery-white. hopefully this ? i didn't fully understand the question

this would be called the responsiveness