What kind of tissue transmits signals across a synapse

That is no tissue. Its called the synaptic cleft. There is a lubricant sustance in it   but it is not called tissue!

Neurons

Explanation:

Neurons are a group of cells that transmit signals between themselves by secreting neutransmitters in the snaptic clefts.

the law of original horizontality explains:   why rocks appear in layers. correct answer: b the law suggests that all rock layers are originally laid down (deposited) horizontally and can later be deformed.   the principle is used by geologists to make assumptions about the relative ages of sedimentary rocks.

the last one: artificial selection/genetic engineering

plant breeding is modifying the genetic composition of the plant - but this isn't cloning (which is specifically introducing a gene into a genome). but you are artificially selecting for the phenotype that you want.

the second one is literally genetic engineering - the gene would have been cloned first and then inserted or genetically engineered into the new plant cell (the cotton).