No, there doesn't have to be a direct object or any object at all. Examples:
We ran fast. ('fast' is an adverb modifying the verb 'ran', no object)
I will, she won't. (two subjects, two verbs, no object)
Stop! (the subject 'you' is implied, 'stop' is the verb, no object.)
I was just thinking. ('was thinking' is the verb, 'just' is an adverb modifying the the auxiliary verb 'was', no object)
The verb does not have a direct object in the sentence, "She is insecure."
There is no direct object in that sentence.
There is no direct object in this sentence.
There is no direct object in that sentence.
In the sentence 'you have her a surprise gift', 'her' is an indirect object. 'Gift' is the direct object in that sentence.
A direct object is the someone or something that receives the action of the verb. Identify the verb and ask "What?" or "Whom?" to determine the direct object. "study" is the verb in that sentence. What was studied? "maps" is the direct object.
The verb does not have a direct object in the sentence, "She is insecure."
There is no direct object in that sentence.
There is no direct object in that sentence.
A direct object can usually be made into the subject of a corresponding passive sentence. E.g., for part of the question asked, a passive form would be "A direct object is not contained by a sentence" which shows that in the original, "a direct object" is the direct object of "contain". So if a noun phrase immediately following the verb cannot be made the subject of a corresponding passive, that is evidence that the noun phrase is not a direct object. For instance, "a ghost" is not a direct object in "I am now a ghost", since you cannot form a passive construction *"A ghost is now been by me." Likewise, "a fish" is not a direct object in "He became a fish", because *"A fish was become by him" is no good.
There is no direct object in that sentence.
There is no direct object in this sentence.
In the sentence 'you have her a surprise gift', 'her' is an indirect object. 'Gift' is the direct object in that sentence.
Yes, and very often. Example: "This sentence has a direct object." where object is the D.O.
That sentence does not contain a direct object.
"song" is the direct object in that sentence.
Personality is the direct object in that sentence.