Explanation:

- Section 139: This section addresses the cross-examination of a witness. It specifies that a witness called to produce a document does not become a witness for all purposes simply due to document production.

- Section 140: This section specifically deals with witnesses regarding character. It clarifies how character evidence may be used in trials, whether to support or attack credibility.

- Section 145: This section is about cross-examinations, particularly when questioning a witness about prior written statements.

- Section 163: This covers the issue of giving false evidence or representations by witnesses.