A transition is a word or phrase that
is used in describing transportation or travel
concludes a paragraph by summarizing main ideas
captures readers' attention and stirs readers' interest
unifies ideas by signaling a relationship between the ideas

A transition is a word or phrase that unifies ideas by signaling a relationship between the ideas.

Explanation:

A speech can be classified into four main parts:

i)Introduction

ii)Body

iii)Transitions

iv)Conclusion

Transition refers to the words, phrases or paragraphs to move from the introduction part of the speech to the body. In simple, transition means moving from one point to the next.

A word or phrase is used throughout the speech to link the parts of the speech together. Transition helps the speaker to move smoothly and clearly from the intro to the body. It also helps in exiting from one part of the speech and moving to conclusion.

your awnser would be b.