Answer: A) the existence of unpaired electrons in the valence shell Explanation: When atoms react they do so in order to reach the lowest energy, which is the most stable. The electrons orbitals will overlap in the way that reduces the energy the most. Orbitals of similar energy will produce the greatest stabilisation.The answer you gave isn't the whole story, it depends what species is reacting with what. The effective nuclear charge on the atom will affect the energy of the valance electrons.   Hence, the reactivity of an atom arises from the existence of unpaired electrons in the valence shell.

Answer: B) Half year Explanation: 3300 ----- 3% ↑ (1st time interval, 99) → 3399. Here, time interval is given as half-yearly i.e. 6 months.

Answer: A) 600 Explanation: Two men, three women and one child can be selected in ⁴C₂ x ⁶C₃ x ⁵C₁ ways = 600 ways.

Answer: D) 44 & 28 Explanation: Letx = peacocks y = deers 2x + 4y = 200 x + y = 72 y = 72 - x 2x + 288 - 4x = 200 x = 44 peacocks y = 28 deers

Answer: C) 2029 Explanation: How to find the years which have the same Calendars :   Leap year calendar repeats every 28 years. Here 28 is distributed as 6 + 11 + 11.   Rules: a) If given year is at 1st position after Leap year then next repeated calendar year is Givenyear+6. b) If given year is at 2nd position after Leap year then next repeated calendar year is Givenyear+11. c) If given year is at 3rd position after Leap year then next repeated calendar year is Givenyear+11.   Now, the given year is 2018 We know that 2016 is a Leap year. 2016    2017    2018    2019  2020 Lp Y      1st     2nd      3rd     Lp Y   Here 2018 is at 2 nd position after the Leap year. According to rule b) the calendar of 2018 is repeated for the year is 2018 + 11 = 2029.

Here in the alphabets the letter U is missing and it represents the word MISSING YOU (U).

Answer: C) Backup file Explanation: In computing, ".bak" is a filename extension commonly used to signify a backup copy of a file.

Answer: D) personal income taxes Explanation: The largest proportion of federal revenues comes from personal income taxes. Almost half of all federal revenue (47 percent) comes from individual income taxes.