Subject   +                         Aux. Verb     +     Main Verb    +   by + ---

↓                                             ↓                            ↓                         ↓

Many accidents                 (be)  are                 caused                    by--------

                                                                                 ↓

                                                                  (Past Participle)

It is also a general statement, hence, the Aux. Verb will be used in Simple Present Tense.

Hence, many accidents are caused by reckless driving is the right usage.

by will replace with because – by (Prep.) is used for indicating the agent/object after a Passive Verb Agent/Object → his friend Passive Verb → accompanied With (Prep.) indicates being in the company of Look at the examples given below : His friend stayed with him in the hospital. He was knocked down by a bus. Hence, by his friend is the right usage.

for will replace since because – for (Prep.) indicates a length of time Since (Prep.) indicates a past time until a later time, or until now Look at the examples given below : I have lived in Bangalore for twenty-five years. I had been living in Bangalore since 1964. Hence, for ten years before moving to their present house is the right usage.

either will be used after tell me because either — or is the right pair of correlative Conjunction like neither — nor. It shows a relationship between two things or two situations. Either comes after the Verb when the two actions mentioned are similar (they share the same Verb) Either comes before the Verb when the two actions mentioned are different. Look at the examples given below : She wants to play either tennis or volleyball. She wants to either go shopping or relax in the park. Hence, you must tell me either is the right usage.

In/from will replace into because – in (Prep.) is used for indicating within a place from (Prep.) is used for indicating source/origin into (Prep.) is used for indicating entry, inclusion, or introduction in a place Look at the examples given below : He walked into the room. The train was coming from Australia. They were bringing drugs in India, for which they were punished. Prosecute (Verb) : to officially charge somebody with a crime in court Hence, in/from Australia is the right usage.

more will replace much because – more (Adv.) : in addition; to a greater extent (needs to be done/is desired) more → Comparative Degree much →Positive Degree most →Superlative Degree Look at the examples given below : People watch T.V. more than is needed. She needs to be given more time than is allotted. Hence, leaves more to be desired is the right usage.

at will replace to because – We usually say that someone arrives at a place/arrives in a country/city Look at the examples given below: We arrived at the station at 3 o'clock. The President arrived in Rome today. Use of arrive to is incorrect. Hence, at our destination is the right usage.