Slowest means of communication is Inland Letter

Explanation:
The slowest means of communication out of the given options is the Inland Letter. Here is a detailed explanation of each option:

a) Inland Letter:
An inland letter is a traditional form of communication where a physical letter is sent from one location to another within the same country. It requires the use of postal services for delivery. Inland letters are typically delivered through regular mail services, which can take several days or even weeks, depending on the distance and efficiency of the postal system. Therefore, it is the slowest means of communication among the given options.

b) Speed Post:
Speed Post, on the other hand, is a premium postal service that offers faster delivery compared to regular mail. It is a reliable and time-bound service provided by postal authorities. Speed Post ensures quicker delivery of letters and parcels, usually within 1-7 working days, depending on the destination. It is faster than an inland letter and provides a tracking facility to monitor the progress of the delivery.

c) Email:
Email is a digital means of communication that allows users to send messages electronically. It is one of the fastest methods of communication available today. Emails are sent and received almost instantly, regardless of the distance between the sender and the recipient. However, the speed of email delivery can also depend on factors like internet connection and server performance.

d) Phone:
Phone communication refers to the use of telephones or mobile devices to have a conversation in real-time. It involves the transmission of voice signals through telecommunication networks. Phone communication is generally considered faster than postal services, as it allows for immediate interaction and response between individuals. However, it may still involve some delays due to factors like network congestion or call connectivity issues.

In conclusion, the slowest means of communication among the given options is the Inland Letter, as it relies on physical mail delivery through regular postal services, which can be slower compared to the other options.