Clarity of speech, remaining calm and focused, being polite and following some basic rules of etiquette will all aid the process of .

Verbal

Explanation: All the skills given above are essential and braces the process of verbal communication. However, it is often taken as oral or spoken mode of communication yet it contains both the written and the spoken as verbal communication implies the usage of words to communicate, be it spoken or written. For an effective verbal communication, it is essential to be very clear not mere with your thoughts while delivering a speech but also with the clarity of speech as you would be interpreted on the basis of what you speak. secondly, remaining calm during the communication will back you to express the thoughts profitably and being focused is required or else one may deviate from the topic. Following some basic ettiquette and active listening will help to add cherry on the cake in triumphantly delivering your ideas and thoughts through your communication.  

b,c,

a) he encouraged islamic schools to introduce greek texts.

d) he invited greek scholars to teach their texts to the locals.

explanation: