Explanation:
In this question, the correct answer is option 'B' - "I've spoken to him on the telephone last month." Let's break down the options and understand why the other options are incorrect.

a) I spoke:
This option is incorrect because it uses the past tense "spoke" without any auxiliary verb. In English, we use the present perfect tense to talk about past actions that are still relevant or have an impact on the present. Therefore, using the simple past tense "spoke" is not appropriate in this context.

c) I didn't spoke:
This option is incorrect because it uses the incorrect negation of the verb. In English, when negating a verb in the past tense, we use the auxiliary verb "did" along with the base form of the main verb. However, the base form of the verb "speak" is "speak" itself, not "spoke." Therefore, the correct negation would be "I didn't speak," but this option still doesn't use the appropriate tense for the given context.

d) I speaked:
This option is incorrect because "speaked" is not a valid past tense form of the verb "speak." The correct past tense form of "speak" is "spoke." Therefore, this option is grammatically incorrect.

b) I've spoken:
This option is correct because it uses the present perfect tense, which is the appropriate tense for talking about a past action that is still relevant to the present. The present perfect tense is formed using the auxiliary verb "have" (in this case, "I've" is a contraction of "I have") followed by the past participle form of the main verb, which is "spoken" in this case.

Conclusion:
Based on the explanations above, option 'B' - "I've spoken to him on the telephone last month" is the correct answer. It uses the present perfect tense correctly and is the most appropriate choice among the given options.