Explanation/Reference:
Explanation:
C: During the first execution of a SQL statement, an execution plan is generated as usual.
D: if multi-column statistics are not present for the relevant combination of columns, the optimizer can fall back on cardinality feedback.
(not B)* Cardinality feedback. This feature, enabled by default in 11.2, is intended to improve plans for repeated executions.
optimizer_dynamic_sampling
optimizer_features_enable
* dynamic sampling or multi-column statistics allow the optimizer to more accurately estimate selectivity of conjunctive predicates.
Note:
* OPTIMIZER_DYNAMIC_SAMPLING controls the level of dynamic sampling performed by the optimizer.
Range of values. 0 to 10
* Cardinality feedback was introduced in Oracle Database 11gR2. The purpose of this feature is to automatically improve plans for queries that are executed repeatedly, for which the optimizer does not estimate cardinalities in the plan properly. The optimizer may misestimate cardinalities for a variety of reasons, such as missing or inaccurate statistics, or complex predicates. Whatever the reason for the misestimate, cardinality feedback may be able to help.

A: The APPEND keyword tells SQL*Loader to preserve any preexisting data in the table.
Other options allow you to delete preexisting data, or to fail with an error if the table is not empty to begin with.
B (not D):
Note:
* SQL*Loader-00210: first data file is empty, cannot process the FIELD NAMES record Cause: The data file listed in the next message was empty. Therefore, the FIELD NAMES FIRST FILE directive could not be processed.
Action: Check the listed data file and fix it. Then retry the operation E:
* A comma-separated values (CSV) (also sometimes called character-separated values, because the separator character does not have to be a comma) file stores tabular data (numbers and text) in plain-text form. Plain text means that the file is a sequence of characters, with no data that has to be interpreted instead, as binary numbers. A CSV file consists of any number of records, separated by line breaks of some kind; each record consists of fields, separated by some other character or string, most commonly a literal comma or tab. Usually, all records have an identical sequence of fields.
* Fields with embedded commas must be quoted.
Example:
1 997,Ford,E350,"Super, luxurious truck"
Note:
* SQL*Loader is a bulk loader utility used for moving data from external files into the Oracle database.

Explanation/Reference:
Explanation:
Note:
Providing a UNIX Group Name
If you are installing a product on a UNIX system, the Installer will also prompt you to provide the name of the group which should own the base directory.
You must choose a UNIX group name which will have permissions to update, install, and deinstall Oracle software. Members of this group must have write permissions to the base directory chosen.
Only users who belong to this group are able to install or deinstall software on this machine.