The correct answer is A. ALTER SHARE .
To provide a consumer account with access to an existing share, the provider adds the consumer account to the share. This is done using the ALTER SHARE command with the ADD ACCOUNTS clause.
Example:
ALTER SHARE my_share
ADD ACCOUNTS = consumer_org.consumer_account;
Why A is correct:
ALTER SHARE modifies an existing share. Adding consumer accounts to a share gives those accounts access to the share.
Why the other options are incorrect:
B). CREATE SHARE creates a new share object, but it does not by itself add a consumer account to an existing share.
C). DESCRIBE SHARE displays metadata about a share; it does not grant access.
D). GRANT < privilege > ... TO SHARE grants database object privileges to the share, such as usage on a database or select on a table. It does not add a consumer account to the share.
Official Snowflake documentation reference:
Snowflake documentation explains that ALTER SHARE ... ADD ACCOUNTS is used to add consumer accounts to a share. Object privileges are granted separately to the share using GRANT ... TO SHARE.
Reference: Snowflake Documentation - ALTER SHARE; Snowflake Documentation - Secure Data Sharing; Snowflake Documentation - GRANT ... TO SHARE; SnowPro Core Study Guide - Data Protection and Governance.

One of the characteristics of materialized views in Snowflake is that they allow multiple tables to be joined in the underlying query. This enables the pre-computation of complex queries involving joins, which can significantly improve the performance of subsequent queries that access the materialized view4. Reference: [COF-C02] SnowPro Core Certification Exam Study Guide

For the ALLOWED VALUES tag property, the maximum number of possible string values for a single tag is
256. This allows for a wide range of values to be assigned to a tag when it is set on an object

A Stream object in Snowflake is used for change data capture (CDC), which records data manipulation language (DML) changes made to tables, including inserts, updates, and deletes3.