It is I who … to blame for the lapses.

1. Analyze the question The sentence is "It is I who ___ to blame for the lapses." We need the correct verb form. This tests concord (subject-verb agreement) with relative pronouns.

2. Explain the concept In a sentence like "It is I who...", the relative pronoun who takes its person and number from its antecedent, the word it refers to. Here, the antecedent is I (first person singular). So the verb after "who" must agree with "I".

3. Step-by-step solution

• Antecedent of "who": I (first person singular)
• Verb form needed with "I" in the present tense: am
• The main clause "It is I" is in the present tense, so the verb should also be present. This rules out was.
• is would suit he/she/it, and are would suit you/we/they. Neither agrees with "I".

Complete sentence: It is I who am to blame for the lapses.

4. Answer The correct option is B. am.

5. Tip In "It is I/you/we who ___", always ask: "Who is 'who' pointing to?" The verb after "who" agrees with that word.

• It is you who are late.
• It is he who is late.
• It is I who am late.